Compositions and methods for enhanced sensitivity and specificity of nucleic acid synthesis

ABSTRACT

The present invention relates to nucleic acid inhibitors, compositions and method for enhancing synthesis of nucleic acid molecules. In a preferred aspect, the invention relates to inhibition or control of nucleic acid synthesis, sequencing or amplification. Specifically, the present invention discloses nucleic acids having affinity for polypeptides with polymerase activity for use in such synthesis, amplification or sequencing reactions. The nucleic acid inhibitors are capable of inhibiting nonspecific nucleic acid synthesis under certain conditions (e.g., at ambient temperatures). Thus, in a preferred aspect, the invention relates to “hot start” synthesis of nucleic acid molecules. Accordingly, the invention prevents, reduces or substantially reduces nonspecific nucleic acid synthesis. The invention also relates to kits for synthesizing, amplifying, reverse transcribing or sequencing nucleic acid molecules comprising one or more of the nucleic acid inhibitors or compositions of the invention. The invention also relates to using the inhibitors of the invention to prevent viral replication or treat viral infections in a subject. Thus, the invention relates to therapeutic methods and pharmaceutical compositions using the inhibitors of the invention. The invention thus may be used for in vivo and in vitro inhibition of nucleic acid synthesis and/or inhibition of polymerase activity.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is related to U.S. provisional patent application No.60/142,072 filed Jul. 2, 1999, which is specifically incorporated hereinin its entirety.

FIELD OF THE INVENTION

The present invention relates to a method for increasing sensitivity andspecificity of nucleic acid synthesis by reducing nonspecific nucleicacid synthesis occurring at ambient temperature. The invention alsorelates to novel nucleic acids which have high affinity to polymerases.The methods and compositions of the present invention can be used in DNAsequencing, amplification reactions, nucleic acid synthesis and cDNAsynthesis.

The invention also relates to nucleic acids and compositions which arecapable of inhibiting or preventing nucleic acid synthesis, sequencing,amplification and cDNA synthesis, for example, by binding one or morepolypeptides with polymerase activity. In addition, the materials andmethods of the present invention may be used as therapeutics to inhibitthe replication of organisms that rely upon a reverse transcriptaseactivity for completion of their life cycle, such as retroviruses. Theinvention also relates to vectors and host cells comprising such nucleicacid molecules. The invention also concerns kits comprising thecompositions or nucleic acids of the invention.

BACKGROUND OF THE INVENTION

DNA polymerases synthesize the formation of DNA molecules which arecomplementary to a DNA template. Upon hybridization of a primer to thesingle-stranded DNA template, polymerases synthesize DNA in the 5′ to 3′direction, successively adding nucleotides to the 3′-hydroxyl group ofthe growing strand. Thus, in the presence of deoxyribonucleosidetriphosphates (dNTPs) and a primer, a new DNA molecule, complementary tothe single stranded DNA template, can be synthesized.

Both mesophilic and thermophilic DNA polymerases are used to synthesizenucleic acids. Using thermostable rather than mesophilic polymerases ispreferable since the higher annealing temperatures used withthermostable polymerases result in less non-specific DNA amplificationfrom extension of mis-annealed primers. Even with thermostablepolymerases, however, some primer sequences and certain experimentalconditions can result in the synthesis of a significant amount ofnon-specific DNA products. These non-specific products can reduce thesensitivity of polymerase-based assays and can require extensiveoptimization for each primer set. In addition, this problem isintensified when polymerases having a high level of activity at ambienttemperature are employed (for example, DNA polymerase from Thermotoganeapolitana).

In examining the structure and physiology of an organism, tissue orcell, it is often desirable to determine its genetic content. Thegenetic framework of an organism is encoded in the double-strandedsequence of nucleotide bases in the deoxyribonucleic acid (DNA) which iscontained in the somatic and germ cells of the organism. The geneticcontent of a particular segment of DNA, or gene, is only manifested uponproduction of the protein and RNA which the gene encodes. In order toproduce a protein, a complementary copy of one strand of the DNA doublehelix (the “coding” strand) is produced by polymerase enzymes, resultingin a specific sequence of ribonucleic acid (RNA). This particular typeof RNA, since it contains the genetic message from the DNA forproduction of a protein, is called messenger RNA (mRNA).

Within a given cell, tissue or organism, there exist many mRNA species,each encoding a separate and specific protein. This fact provides apowerful tool to investigators interested in studying genetic expressionin a tissue or cell. mRNA molecules may be isolated and furthermanipulated by various molecular biological techniques, thereby allowingthe elucidation of the full functional genetic content of a cell, tissueor organism.

A common approach to the study of gene expression is the production ofcomplementary DNA (cDNA) clones. In this technique, the mRNA moleculesfrom an organism are isolated from an extract of the cells or tissues ofthe organism. This isolation often employs chromatography matrices, suchas cellulose or agarose, to which oligomers of thymidine (T) have beencomplexed. Since the 3′ termini on most eukaryotic mRNA moleculescontain a string of Adenosine (A) bases, and since A binds to T, themRNA molecules can be rapidly purified from other molecules andsubstances in the tissue or cell extract. From these purified mRNAmolecules, cDNA copies may be made using the enzyme reversetranscriptase (RT) or DNA polymerases having RT activity, which resultsin the production of single-stranded cDNA molecules. The single-strandedcDNAs may then be converted into a complete double-stranded DNA copy(i.e., a double-stranded cDNA) of the original mRNA (and thus of theoriginal double-stranded DNA sequences, encoding this mRNA, contained inthe genome of the organism) by the action of a DNA polymerase. Theprotein-specific double-stranded cDNAs can then be inserted into avector, which is then introduced into a host bacterial, yeast, animal orplant cell, a process referred to as transformation or transfection. Thehost cells are then grown in culture media, resulting in a population ofhost cells containing (or in many cases, expressing) the gene ofinterest or portions of the gene of interest.

This entire process, from isolation of mRNA to insertion of the cDNAinto a vector (e.g., plasmid, viral vector, cosmid, etc.) to growth ofhost cell populations containing the isolated gene or gene portions, istermed “cDNA cloning.” If cDNAs are prepared from a number of differentmRNAs, the resulting set of cDNAs is called a “cDNA library,” anappropriate term since the set of cDNAs represents a “population” ofgenes or portions of genes comprising the functional genetic informationpresent in the source cell, tissue or organism.

Synthesis of a cDNA molecule initiates at or near the 3′ termini of themRNA molecules and proceeds in the 5′-to-3′ direction successivelyadding nucleotides to the growing strand. Priming of the cDNA synthesisat the 3′-termini at the poly A tail using an oligo (dT) primer ensuresthat the 3′ message of the mRNAs will be represented in the cDNAmolecules produced. The ability to increase sensitivity and specificityduring cDNA synthesis provides more representative cDNA libraries andmay increase the likelihood of the cDNA library having full-length cDNAmolecules (e.g., full-length genes). Such advances would greatly improvethe probability of finding full-length genes of interest.

In addition to their importance for research purposes, reversetranscriptase enzymes play a critical role in the life cycle of manyimportant pathogenic viruses, in particular, the human immunodeficiencyviruses (HIV). In order to complete its life cycle, HIV and othersimilar viruses must use a reserve transcriptase enzyme to convert theviral RNA genome into DNA for integration into the host's genomicmaterial. Since this step is critical to the viral life cycle and hostcells do not have any similar requirement for reverse transcriptaseactivity, the reverse transcriptase enzyme has been intensively studiedas a chemotherapeutic target. In general, the bulk of therapeuticreagents directed at the reverse transcriptase enzyme have beennucleotide analogues, for example AZT. Other therapeutic modalitiesusing oligonucleotide-based reagents, e.g., anti-sense oligonucleotidesand ribozymes, have been used to inhibit viral replication, however,these reagents are not targeted specifically against reversetranscriptase activity, instead of being targeted against the nucleicacid of the viral genome. See, for example, Goodchild, et al.,“Inhibition of human immunodeficiency virus replication by antisenseoligodeoxynucleotides,” Proc. Natl. Acad. Sci. USA 85:5507-5511 (1988),Matsukara, et al., “Regulation of viral expression of humanimmunodeficiency virus in vitro by an antisense phosphorothioateoligodeoxynucleotide against rev (art/trs) in chronically infectedcells,” Proc. Natl. Acad Sci. USA 86:4244-4248 (1989), Rossi, et al.,“Ribozymes as Anti-HIV-1 Therapeutic Agents: Principles, Applications,and Problems,” Aids Research and Human Retroviruses 8:183:189 (1992),Goodchild, “Enhancement of ribozyme catalytic activity by a contiguousoligodeoxynucleotide (facilitator) and by 2′-O-methylation,” NucleicAcids Research 20:4607-4612 (1992) and Kinchington, et al., “Acomparison of gag, pol and rev antisense oligodeoxynucleotides asinhibitors of HIV-1,” Antiviral Research 17:53-62 (1992) which arespecifically incorporated herein by reference. Oligonucleotides thathave been blocked at the 3′-end to prevent their elongation by reversetranscriptase have also been considered as inhibitors (see, for example,Austermann, et al., “Inhibition of human immunodeficiency virus type 1reverse transcriptase by 3′-blocked oligonucleotides” BiochemicalPharmacology 43(12):2581-2589 (1992). Each of the above cited referencesis specifically incorporated herein in its entirety.

Oligonucleotides have been investigated for anti-HIV activity. Forexample, Idriss, et al. (1994), Journal of Enzyme Inhibition 8(2)97-112,disclose DNA oligonucleotides in a hairpin structure as inhibitors ofHIV RT activity while Kuwasaki, et al., (1996) Biochemical andBiophysical Research Communications 228:623-631 disclose anti-sensehairpin oligonucleotides containing a mixture of deoxy and2′-methoxy-nucleotides with anti-HIV activity.

Notwithstanding these and other efforts to modulate the activity ofpolymerases, there remains a need in the art for materials and methodsto prevent the undesirable activity of the polymerases while permittingthe synthesis of nucleic acids by the polymerase when such synthesis isdesired. These and other needs are met by the present invention.

SUMMARY OF THE INVENTION

The present invention provides materials and methods for inhibiting,reducing, substantially reducing or eliminating nucleic acid synthesisunder certain conditions (preferably at ambient temperatures and/orwithin a cell) while permitting synthesis when such synthesis isdesired.

In a preferred aspect, the invention relates to methods for theprevention or inhibition of nucleic acid synthesis during reaction setup (e.g., in vitro) and preferably before optimum reaction conditionsfor nucleic acid synthesis are achieved. Such inhibition of synthesis atsub-optimum conditions or during reaction set up prevents or reducesnon-specific nucleic acid synthesis. Once reaction set up is completeand the optimum conditions are reached, nucleic acid synthesis can beinitiated.

In another aspect, the present invention relates to a method ofinhibiting a polymerase enzyme within a cell (e.g., in vivo) byintroducing into the cell an oligonucleotide or inhibitor of theinvention, preferably said oligonucleotide comprises a 5′- and a3′-portion, wherein the said 3′-portion comprises one or moredeoxyribonucleotides or derivatives thereof and said 5′-portioncomprises one or more ribonucleotides or derivatives thereof and whereinall or a portion of said 3′-portion is capable of base pairing to all ora portion of said 5′-portion and incubating said cell under conditionscausing the inhibition of the polymerase. In some embodiments, the5′-portion of the oligonucleotide which comprises ribonucleotides formsa 5′-overhang. In another aspect, the oligonucleotide is in the form ofa hairpin and preferably the stem of the hairpin comprises a series ofcontiguous ribonucleotides based paired or hybridized with a series ofcontinguous deoxyribonucleotides. In some embodiments the polymerase isa reverse transcriptase and may preferably be an HIV reversetranscriptase.

In another aspect, the present invention provides a method of inhibitingreplication of a virus, by providing a virus, said virus comprising areverse transcriptase and requiring activity of the reversetranscriptase for replication and contacting said reverse transcriptasewith an oligonucleotide or inhibitor of the invention that inhibitsactivity of said reverse transcriptase thereby inhibiting replication ofsaid virus. In some embodiments, the oligonucleotide comprises a 5′- anda 3′-portion, wherein said 3′-portion comprises one or moredeoxyribonucleotides or derivatives thereof and said 5′-portioncomprises one or more ribonucleotides or derivatives thereof and whereinall or a portion of said 3′-portion is capable of base pairing to all ora portion of said 5′-portion. In some embodiments, the 5′-portion of theoligonucleotide which comprises ribonucleotides forms a 5′-overhang. Inanother aspect, the oligonucleotide is in the form of a hairpin andpreferably the stem of the hairpin comprises a series of contiguousribonucleotides base paired or hybridized with a series of contiguousdeoxyribonucleotides. In some embodiments, the virus is an HIV. In someembodiments, contacting comprises introducing said oligonucleotide intoa cell.

More specifically, the invention relates to controlling nucleic acidsynthesis by introducing an inhibitory nucleic acid or oligonucleotidewhich binds to or interacts with the polypeptide with polymeraseactivity (e.g., DNA polymerases, reverse transcriptases, etc.).Accordingly, such inhibitory nucleic acids or oligonucleotide can bindthe polymerase and interfere with nucleic acid synthesis by preventingbinding or interaction of the polymerase or reverse transcriptase withthe primer/template. Preferably, such inhibitory nucleic acid moleculesare double stranded molecules although any form of nucleic acid moleculemay be used as long as the molecule can bind or interact with thepolymerization enzyme of interest. Such molecules may be DNA, RNA,DNA/RNA hybrids, double stranded DNA, double stranded RNA and DNA/RNAdouble stranded molecules. Derivative nucleic acid molecules may also beused such as Protein Nucleic Acids (PNAs), linked nucleic acids (LNA,available form Proligo, Boulder Colo.) and nucleic acid moleculescomprising modified nucleotides. Moreover, the nucleic acid moleculesmay be in any form or topology such as linear, circular, supercoiled,double stranded with one or more single stranded portions, hairpinstructure, or complexed with other molecules such as peptides orproteins and the like. Such inhibitory nucleic acids preferably includedouble-stranded nucleic acid molecules (which may comprise one or moreinternal, 5′ and/or 3′ single stranded portions), or single strandednucleic acid molecules capable of folding into a double stranded form,i.e. forming one or more hairpin-loops, such that at least one doublestranded portion of the nucleic acid molecule is capable of binding to apolypeptide with polymerase activity. In one aspect, the nucleic acidmolecules used in the invention bind the polypeptide having polymeraseactivity (e.g., DNA polymerase, reverse transcriptase, etc.) with highaffinity. Once the polymerase or reverse transcriptase is complexed withthe inhibitory nucleic acid, it is unavailable for annealing to theprimer/template substrate, resulting in reduced, substantially reduced,or no polymerase or reverse transcriptase activity. In some embodiments,the oligonucleotides of the present invention may comprise a 5′- and a3′-portion, wherein said 3′-portion comprises one or moredeoxyribonucleotides or derivatives thereof and said 5′-portioncomprises one or more ribonucleotides or derivatives thereof and whereinall or a portion of said 3′-portion is capable of base pairing to all ora portion of said 5′-portion. In some embodiments, the oligonucleotidesof the invention may comprise a 5′-portion, wherein said 5′-portioncomprising ribonucleotides forms a 5′-overhang. In some embodiments, anoligonucleotide of the invention may comprise one or more modificationsso as to be non-extendable. In some embodiments, this modification maybe to the 3′-most nucleotide. In some embodiments, the modification isphosphorylation of the 3′-most nucleotide at the 3′-hydroxyl. Anoligonucleotide of the present invention may comprise one or moremodifications so as to be resistant to digestion or degradation by, forexample, one or more nucleases. In some embodiments, this modificationmay be the incorporation of one or more phophorothioate moieties. Insome embodiments, the modification may comprise alkylation of one ormore hydroxl groups.

Thus, the inhibitory nucleic acid is preferably introduced into thereaction mixture where it competitively binds to or interacts with thepolymerase, thereby inhibiting synthesis by the polymerase underparticular reaction conditions. Thus, interaction or binding of theinhibitor and polymerase preferably results in the formation of aninhibitor/polymerase complex.

The inhibition of polymerase activity or nucleic acid synthesis by thenucleic acids of the invention is preferably reduced, substantiallyreduced, inhibited, or eliminated so that nucleic acid synthesis mayproceed when reaction conditions are changed, for example, when thetemperature is raised. In a preferred aspect, the changed conditionsaffect the ability of the inhibitory nucleic acids to interact with thepolymerase causing release of the polymerase and/or denaturation orinactivation of the inhibitory nucleic acids making the polymeraseavailable thus allowing nucleic acid synthesis to proceed. In oneaspect, the inhibitory nucleic acids and the primer/template substratecompetitively interact with the polymerase to prevent synthesis. Underthe changed conditions, the competitive interaction is reduced such thatnucleic acid synthesis occurs. In another aspect, the changed conditionscause the double stranded inhibitory nucleic acid molecule(s) (includinghairpins) to denature or melt such that single stranded molecules areformed which do not substantially bind or interact with the polymerase.In another aspect, a second change in conditions (i.e., temperature islowered to, for example, ambient temperatures) allows the inhibitornucleic acid molecules of the invention to reactivate or again inhibitnucleic acid synthesis. That is, the inhibitors may again interact orbind with the polymerase or reverse transcriptase under the changedconditions. For example, the changed conditions may allow the inhibitorto form double stranded molecules which effectively enhances its bindingor interacting capacity with the polymerase or reverse transcriptases.Thus, in accordance with the invention, the inhibitors may be reused orrecycleable during synthesis reactions (single or multiple) which mayrequire multiple adjustment or changes in reaction conditions (i.e.,temperature changes), without the need to add additional inhibitor.

The invention therefore relates to a method for synthesizing one or morenucleic acid molecules, comprising (a) mixing one or more nucleic acidtemplates (which may be a DNA molecule such as a cDNA molecule, or anRNA molecule such as an mRNA molecule) with one or more primers, and oneor more inhibitory nucleic acids or compositions of the presentinvention capable of binding or interacting with an enzyme havingpolymerase activity, and (b) incubating the mixture in the presence ofone or more enzymes having nucleic acid polymerase activity (e.g., DNApolymerases or reverse transcriptases) under conditions sufficient tosynthesize one or more first nucleic acid molecules complementary to allor a portion of the templates. Alternatively, the method may comprisemixing one or more inhibitor nucleic acids with one or more polymerasesand incubating such mixtures under conditions sufficient to synthesizeone or more nucleic acid molecules. Such conditions may involve the useof one or more nucleotides and one or more nucleic acid synthesisbuffers. Such methods of the invention may optionally comprise one ormore additional steps, such as incubating the synthesized first nucleicacid molecule under conditions sufficient to make a second nucleic acidmolecule complementary to all or a portion of the first nucleic acidmolecule. These additional steps may also comprise the use of theinhibitory nucleic acid molecules of the invention. The invention alsorelates to nucleic acid molecules synthesized by these methods.

In a related aspect, the nucleic acid synthesis method may comprise (a)mixing one or more polymerases with one or more of the inhibitorynucleic acid molecules of the invention, and (b) incubating such mixtureunder conditions sufficient to inactivate or substantially inhibit orreduce polymerase activity of such polymerases. In another aspect, suchincubation is under conditions sufficient to inhibit or prevent suchnucleic acid synthesis.

The invention also relates to a method for amplifying one or morenucleic acid molecules, comprising (a) mixing one or more nucleic acidtemplates with one or more primers, and one or more inhibitory nucleicacid molecules or compositions of the present invention capable ofbinding or interacting with an enzyme having polymerase activity and (b)incubating the mixture in the presence of one or more enzymes havingnucleic acid polymerase activity (e.g., DNA polymerases) underconditions sufficient to amplify one or more nucleic acid moleculescomplementary to all or a portion of the templates. More specifically,the invention relates to a method of amplifying a DNA moleculecomprising: (a) providing a first and second primer, wherein said firstprimer is complementary to a sequence within or at or near the3′-termini of the first strand of said DNA molecule and said secondprimer is complementary to a sequence within or at or near the3′-termini of the second strand of said DNA molecule, and one or moreinhibitory nucleic acids or compositions of the invention (e.g., anucleic acid having affinity for an enzyme with polymerase activity);(b) hybridizing said first primer to said first strand and said secondprimer to said second strand; (c) incubating the mixture underconditions such that a third DNA molecule complementary to all or aportion of said first strand and a fourth DNA molecule complementary toall or a portion of said second strand are synthesized; (d) denaturingsaid first and third strand, and said second and fourth strands; and (e)repeating steps (a) to (c) or (d) one or more times. Such conditions mayinclude incubation in the presence of one or more polymerases, one ormore nucleotides and/or one or more buffering salts. The invention alsorelates to nucleic acid molecules amplified by these methods.

In a related aspect, the nucleic acid amplification method may comprise(a) mixing one or more polymerases with one or more of the inhibitorynucleic acid molecules of the invention, and (b) incubating such mixtureunder conditions sufficient to inactivate or substantially inhibit orreduce polymerase activity of such polymerases. In another aspect, suchincubation is under conditions sufficient to inhibit or prevent suchnucleic acid amplification.

The invention also relates to methods for sequencing a nucleic acidmolecule comprising (a) mixing a nucleic acid molecule to be sequencedwith one or more primers, one or more of the inhibitory nucleic acids orcompositions of the invention, one or more nucleotides and one or moreterminating agents to form a mixture; (b) incubating the mixture underconditions sufficient to synthesize a population of moleculescomplementary to all or a portion of the molecule to be sequenced; and(c) separating the population to determine the nucleotide sequences ofall or a portion of the molecule to be sequenced. The invention morespecifically relates to a method of sequencing a nucleic acid molecule,comprising: (a) providing an inhibitory nucleic acid or composition ofthe present invention (to which an enzyme with polymerase activity asaffinity), one or more nucleotides, and one or more terminating agents;(b) hybridizing a primer to a first nucleic acid molecule; (c)incubating the mixture of step (b) under conditions sufficient tosynthesize a random population of nucleic acid molecules complementaryto said first nucleic acid molecule, wherein said synthesized moleculesare shorter in length than said first molecule and wherein saidsynthesized molecules comprise a terminator nucleotide at their 3′termini; and (d) separating said synthesized molecules by size so thatat least a part of the nucleotide sequences of said first nucleic acidmolecule can be determined. Such terminator nucleotides includedideoxyribonucleoside thiphophates such as ddNTP, ddATP, ddGTP, ddITP orddCTP. Such conditions may include incubation in the presence of one ormore polymerases and/or buffering salts.

In a related aspect, the nucleic acid sequencing method may comprise (a)mixing one or more polymerases with one or more of the inhibitorynucleic acid molecules of the invention, and (b) incubating such mixtureunder conditions sufficient to inactivate or substantially inhibitpolymerase activity of such polymerases. In another aspect, suchincubation is under conditions sufficient to inhibit or prevent suchnucleic acid sequencing.

The invention also relates to the inhibitory nucleic acids of theinvention and to compositions comprising the inhibitory nucleic acids ofthe invention, to vectors (which may be expression vectors) comprisingthese nucleic acid molecules, and to host cells comprising these nucleicacid molecules or vectors. Compositions of the invention may alsoinclude those compositions made for carrying out the methods of theinvention or produced while carrying out such methods. The inventionalso relates to pharmaceutical compositions. Such compositions maycomprise one or more of the inhibitory nucleic acid molecules oroligonucleotides of the invention and at least one other componentselected from the group consisting of one or more nucleotides, one ormore polymerases (e.g., thermophilic or mesophilic DNA polymerasesand/or reverse transcriptases), one or more suitable buffers or buffersalts, one or more primers, one or more terminating agents, one or moreviruses, one or more cells, and one or more amplified or synthesizednucleic acid molecules produced by the methods of the invention. Theinvention also relates to methods of producing an inhibitory nucleicacid comprising culturing the above-described host cells underconditions favoring the production of the nucleic acid by the hostcells, and isolating the nucleic acid. The invention also relates tonucleic acid produced by synthetic methods. Such inhibitory nucleic acidmolecules of the invention may also be made by standard chemicalsynthesis techniques.

In a related aspect, the present invention provides materials andmethods for the in vivo inhibition of polymerase activity. In someembodiments, the present invention provides for the introduction of theinhibitory oligonucleotides of the present invention into an organismthereby inhibiting a polymerase present within the organism. In someembodiments, the polymerase may be a reverse transcriptase, preferably aviral reverse transcriptase. In some embodiments, the present inventionprovides a method for the inhibition of a viral reverse transcriptasecomprising contacting a cell or virus expressing a viral reversetranscriptase with an inhibitory oligonucleotide under conditionscausing the oligonucleotide to inhibit the reverse transcriptiase.Preferably, the oligonucleotide is contacted with the cell underconditions sufficient to have the oligonucleotide taken up by the cellby well known techniques. In some embodiments, the present inventionprovides a method of inhibiting the growth of a virus, comprisingcontacting a cell infected with a virus that requires reversetranscriptase activity to complete its life cycle with an inhibitoryoligonucleotide under conditions causing the oligonucleotide to be takenup by the cell and causing the reverse transcriptase to be inhibitedthereby inhibiting the growth of the virus. In some embodiments, thepresent invention provides a method of treating an organism or subjectinfected with a virus that requires reverse transcriptase activity tocomplete its life cycle comprising contacting an infected cell of theorganism or subject with a composition comprising an inhibitoryoligonucleotide under conditions causing the oligonucleotide to be takenup by the cell and causing the reverse transcriptase to be inhibitedthereby treating the organism.

The invention also relates to kits for use in synthesis, sequencing andamplification of nucleic acid molecules, comprising one or morecontainers containing one or more of the inhibitory nucleic acids orcompositions of the invention. These kits of the invention mayoptionally comprise one or more additional components selected from thegroup consisting of one or more nucleotides, one or more polymerases(e.g., thermophilic or mesophilic DNA polymerases and/or reversetranscriptases), one or more suitable buffers, one or more primers andone or more terminating agents (such as one or more dideoxynucleotides).The invention also relates to kits for inhibiting viral replication orkits for treating viral infections comprising the inhibitory nucleicacids of the invention. Such kits may also comprise instructions orprotocols for carrying out the methods of the invention.

Other preferred embodiments of the present invention will be apparent toone of ordinary skill in light of the following drawings and descriptionof the invention, and of the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1. The activity of Tne DNA polymerase was qualitatively determined.Panel A: determination in the absence of inhibitor A, Panel B:determination in the presence of inhibitor. The five lanes, of eachpanel, from left to right are 15 sec, 30 sec, 1 min, 2 min and 5 mintime points that have elapsed before the reactions were quenced. P and Cdenote the primer position and control lane, respectively. Inhibitor Adid not contain dideoxynucleotide at its termini.

FIG. 2. Amplification of a 2.7 Kb target DNA sequence (pUC19) wasperformed at 5 different dilutions of the template. The target wasamplified by Tne DNA polymerase. Two different concentration of Tnepolymerse (85 nM and (e.g, 1 unit) and 42.5 nM (e.g., 0.5 units)) andthe respective inhibitor B Complexes (using a 150-fold excess hairpin Bover the polymerase concentration) were used for each amplificationcondition. The concentration of the target DNA in lanes 1, 2, 3, 4 & 5is 100 pg, 20 pg, 2 pg, 0.2 pg and 0.02 pg, respectively. Inhibitor Bdid not contain dideoxynucleotide at its termini.

FIG. 3. A 1 Kb, 3 Kb and 5 Kb target DNA sequence (human genomic source)were amplified by Tne (85 nM (e.g., 1 unit) and Taq (e.g., 1 unit)) DNApolymerases as represented in panels A, B, and C respectively. The fourlanes of each panel repersented as a, b, c and d are Tne (+125-foldexcess inhibitor A), Tne (+50-fold excess inhibitor A), Tne (noinhibitor) and Taq (no inhibitor), respectively. Inhibitor A contained a3′-terminal dideoxynucleotide (i.e., ddT).

FIG. 4. The amplification of a 5 and 15 Kb target DNA sequence (humangenomic source) was performed with Tne DNA polymerase (8.5 nM (e.g., 0.1units)). The five panels A, B, C, D and E represent reaction conditions:Tne (no inhibitor), Tne (+50-fold excess inhibitor), Tne (+150-foldexcess inhibitor), Tne (+300-fold excess inhibitor), Tne (+750-foldexcess inhibitor), respectively. The two lanes (a and b) for each panelrepresent amplification of a target size of 5 and 15 Kb. For this assay,the inhibitor B was used which did not contain a terminaldideoxynucleotide.

FIG. 5. The amplification of a 3 Kb target DNA sequence (human genomicsource) was performed with 1 unit Taq DNA polymerase. The three panelsA, B, and C represent reaction conditions: for A and B the same primersequences were used—I) the PCR mix was incubated at 94° C. for 1 min andwas set on ice to force mis-priming. All PCR reactions were set for 30min at 25° C. so as to increase non-specific DNA synthesis. Eachcondition has four lanes-lane a (Taq control), b (Taq+16 nM inhibitor),c (Taq+32 nM inhibitor) and d (Taq+64 nM inhibitor). Inhibitor B wasused which did not contain a terminal dideoxynucleotide.

FIG. 6A is a graph showing the results of polymerase activity assays ofThermoscript™ I in the absence and presence of nucleic acid inhibitorsat ambient temperature (left bar), 37° C. (center bar) and 55° C. (rightbar). TS denotes polymerase reaction initiated by Thermoscript™ I, TS-Ddenotes polymerase reaction initiated by Thermoscript™ I in the presenceof nucleic acid inhibitor D, TS-E denotes polymerase reaction initiatedby Thermoscript™ in the presence of nucleic acid inhibitor E, and TS-Hdenotes polymerase reaction initiated by Thermoscript™ I in the presenceof nucleic acid inhibitor H.

FIG. 6B is a graph showing the results of polymerase activity assays ofThermoscript™ I in the absence and presence of nucleic acid inhibitorsat ambient temperature (left bar), 37° C. (center bar) and 55° C. (rightbar). TS denotes polymerase reaction initiated by Thermoscript™ I, TS-Ddenotes polymerase reaction initiated by Thermoscript™ I in the presenceof nucleic acid inhibitor C, TS-H denotes polymerase reaction initiatedby Thermoscript™ I in the presence of nucleic acid inhibitor H, TS-Edenotes polymerase reaction initiated by Thermoscript™ I in the presenceof nucleic acid inhibitor E, TS-F denotes polymerase reaction initiatedby Thermoscript™ I in the presence of nucleic acid inhibitor F, and TS-Gdenotes polymerase reaction initiated by Thermoscript™ I in the presenceof nucleic acid inhibitor G.

FIG. 7 is a photograph of an agarose gel showing the results ofamplification reactions using a 1.6 kb (A), a 2 kb (B) and a 2.6 kb (C)fragment of the NF2 gene. In each panel, lane a is the amplificationusing Taq polymerase alone, lane b is the amplification reaction in thepresence of inhibitor HPHH4Sspa3 at a molar ratio of 1.2:1 inhibitor:polymerase and lane c is the amplification using Platinum Taq.

FIG. 8 is a bar graph showing the results of a dNTP incorporation assayat the indicated temperatures. At each temperature, the solid blackrectangle reports the results obtained with Taq polymerase alone, thestriped rectangle report the results obtained with inhibitor HPHH4Sspa3at a molar ration of 2:1 inhibitor:polymerase, the white rectanglereport the results obtained with the same inhibitor at a molar ratio of7.5:1 inhibitor:polymerase.

FIG. 9 is a graph showing the dose dependent inhibition of Taqpolymerase by inhibitor present HPHH4Sspa3 present at the indicatedmolar ratios.

DETAILED DESCRIPTION OF THE INVENTION Definitions

In the description that follows, a number of terms used in recombinantDNA technology are utilized extensively. In order to provide a clearerand consistent understanding of the specification and claims, includingthe scope to be given such terms, the following definitions areprovided.

Primer

As used herein, “primer” refers to a single-stranded oligonucleotidethat is extended by covalent bonding of nucleotide monomers duringamplification or polymerization of a DNA molecule.

Template

The term “template” as used herein refers to double-stranded orsingle-stranded nucleic acid molecules which are to be amplified,synthesized or sequenced. In the case of a double-stranded molecule,denaturation of its strands to form a first and second strand ispreferably performed before these molecules may be amplified,synthesized or sequenced, or the double stranded molecule may be useddirectly as a template. For single stranded templates, a primer,complementary to a portion of the template is hybridized underappropriate conditions and one or more polymerases may then synthesize anucleic acid molecule complementary to all or a portion of saidtemplate. Alternatively, for double stranded templates, one or morepromoters (e.g. SP6, T7 or T3 promoters) may be used in combination withone or more polymerases to make nucleic acid molecules complementary toall or a portion of the template. The newly synthesized molecules,according to the invention, may be equal or shorter in length than theoriginal template.

Incorporating

The term “incorporating” as used herein means becoming a part of a DNAand/or RNA molecule or primer.

Amplification

As used herein “amplification” refers to any in vitro method forincreasing the number of copies of a nucleotide sequence with the use ofa polymerase. Nucleic acid amplification results in the incorporation ofnucleotides into a DNA and/or RNA molecule or primer thereby forming anew molecule complementary to a template. The formed nucleic acidmolecule and its template can be used as templates to synthesizeadditional nucleic acid molecules. As used herein, one amplificationreaction may consist of many rounds of replication. DNA amplificationreactions include, for example, polymerase chain reactions (PCR). OnePCR reaction may consist of 5 to 100 “cycles” of denaturation andsynthesis of a DNA molecule.

Nucleotide

As used herein “nucleotide” refers to a base-sugar-phosphatecombination. Nucleotides are monomeric units of a nucleic acid sequence(DNA and RNA). Nucleotides may also include mono-, di- and triphosphateforms of such nucleotides. The term nucleotide includes ribonucleosidetriphosphates ATP, UTP, CTG, GTP and deoxyribonucleoside triphosphatessuch as dATP, dCTP, dITP, dUTP, dGTP, dTTP, or derivatives thereof. Suchderivatives include, for example, [αS]dATP, 7-deaza-dGTP and7-deaza-dATP, and nucleotide derivatives that confer nuclease resistanceon the nucleic acid molecule containing them. The term nucleotide asused herein also refers to dideoxyribonucleoside triphosphates (ddNTPs)and their derivatives. Illustrated examples of dideoxyribonucleosidetriphosphates include, but are not limited to, ddATP, ddCTP, ddGTP,ddITP, and ddTTP. According to the present invention, a “nucleotide” maybe unlabeled or detectably labeled by well known techniques. Detectablelabels include, for example, radioactive isotopes, fluorescent labels,chemiluminescent labels, bioluminescent labels and enzyme labels.

Blocking Agent

“Blocking agent” refers to a nucleotide (or derivatives thereof),modified oligonucleotides and/or one or more other modifications whichare incorporated into the nucleic acid inhibitors of the invention toprevent or inhibit degradation or digestion of such nucleic acidmolecules by nuclease activity. One or multiple blocking agents may beincorporated in the nucleic acid inhibitors of the invention internally,at or near the 3′ termini and/or at or near the 5′ termini of thenucleic acid inhibitors. Preferably, such blocking agents are located,for linear inhibitor nucleic acid molecules, at or near the 3′ terminiand/or at or near the 5′ termini and/or at the preferred cleavageposition of the 5′ to 3′ exonuclease of such molecules (Lyamichev, V.,Brow, M. A. D., and Dahlberg, J. E., (1993) Science, 260, 778-783).Preferably, such blocking agents prevent or inhibit degradation ordigestion of the inhibitor nucleic acid molecules by exonucleaseactivity associated with the polymerase or reverse transcriptase used orthat may be present in the synthesis reaction. For example, blockingagents for the invention prevent degradation or digestion of inhibitornucleic acid molecules by 3′ exonuclease activity and/or 5′ exonucleaseactivity associated with a polymerase (e.g., a DNA polymerase).Preferred blocking agents in accordance with the invention includedideoxynucleotides and their derivatives such as ddATP, ddCTP, ddGTP,ddITP, and ddTTP. Other blocking agents for use in accordance with theinvention include, but are not limited to, AZT, phosphamide backbones(e.g., PNAs), 3′-dNTPs (e.g., Condycepin) or any nucleotide containing ablocking group, preferably at its 3′-position. Such blocking agentspreferably act to inhibit or prevent exonuclease activity (e.g.,3′-exonuclease activity) from altering or digesting the inhibitorynucleic acids of the invention. In some embodiments, the 5′-terminal ofthe oligonucleotides of the present invention may be modified in orderto make them resistant to 5′-to-3′ exonuclease activity. One suchmodification may be to add an addition nucleotide to the 5′-end of theoligonucleotide in a 5′-5′-linkage (see, Koza M. et al., Journal ofOrganic Chemistry 56:3757). This results in at the 5′-end of theoligonucleotide which results in the 5′-end having a 3. In anotheraspect, such blocking agents preferably inhibit or prevent polymeraseactivity of the polymerases from altering or changing (e.g.,incorporating nucleotides) to the inhibitory nucleic acids of theinvention.

Oligonucleotide

As used herein, “oligonucleotide” refers to a synthetic or biologicallyproduced molecule comprising a covalently linked sequence of nucleotideswhich may be joined by a phosphodiester bond between the 3′ position ofthe pentose of one nucleotide and the 5′ position of the pentose of theadjacent nucleotide. Oligonucleotide as used herein is seen to includenatural nucleic acid molecules (i.e., DNA and RNA) as well asnon-natural or derivative molecules such as peptide nucleic acids,phophothioate containing nucleic acids, phosphonate containing nucleicacids and the like. In addition, oligonucleotides of the presentinvention may contain modified or non-naturally occurring sugar residues(i.e., arabainose) and/or modified base residues. Oligonucleotide isseen to encompass derivative molecules such as nucleic acid moleculescomprising various natural nucleotides, derivative nucleotides, modifiednucleotides or combinations thereof. Thus any oligonucleotide or othermolecule useful in the methods of the invention are contemplated by thisdefinition. Oligonucleotides of the present invention may also compriseblocking groups which prevent the interaction of the molecule withparticular proteins, enzymes or substrates.

Hairpin

As used herein, the term “hairpin” is used to indicate the structure ofan oligonucleotide in which one or more portions of the oligonucleotideform base pairs with one or more other portions of the oligonucleotide.When the two portions are base paired to form a double stranded portionof the oligonucleotide, the double stranded portion may be referred toas a stem. Thus, depending on the number of complementary portions used,a number of stems (preferably 1-10) may be formed. Additionally,formation of the one or more stems preferably allows formation of one ormore loop structures in the hairpin molecule. In one aspect, any one ormore of the loop structures may be cut or nicked at one or more siteswithin the loop or loops but preferably at least one loop is not so cutor nicked. The sequence of the oligonucleotide may be selected so as tovary the number of nucleotides which base pair to form the stem fromabout 3 nucleotides to about 100 or more nucleotides, from about 3nucleotides to about 50 nucleotides, from about 3 nucleotides to about25 nucleotides, and from about 3 to about 10 nucleotides. In addition,the sequence of the oligonucleotide may be varied so as to vary thenumber of nucleotides which do not form base pairs from 0 nucleotides toabout 100 or more nucleotides, from 0 nucleotides to about 50nucleotides, from 0 nucleotides to about 25 nucleotides or from 0 toabout 10 nucleotides. The two portions of the oligonucleotide which basepair may be located anywhere or at any number of locations in thesequence of the oligonucleotide. In some embodiments, onebase-pairing-portion of the oligonucleotide may include the 3′-terminalof the oligonucleotide. In some embodiments, one base-pairing-portionmay include the 5′-terminal of the oligonucleotide. In some embodiments,one base-pairing-portion of the oligonucleotide may include the3′-terminal while the other base-pairing-portion may include the5′-terminal and, when base paired, the stem of the oligonucleotide isblunt ended. In other embodiments, the location of the base pairingportions of the oligonucleotide may be selected so as to form a3′-overhang, a 5′-overhang and/or may be selected so that neither the3′- nor the 5′-most nucleotides are involved in base pairing.

Hybridization

The terms “hybridization” and “hybridizing” refer to base pairing of twocomplementary single-stranded nucleic acid molecules (RNA and/or DNAand/or PNA) to give a double-stranded molecule. As used herein, twonucleic acid molecules may be hybridized although the base pairing isnot completely complementary. Accordingly, mismatched bases do notprevent hybridization of two nucleic acid molecules provided thatappropriate conditions, well known in the art, are used. In a preferredaspect, the double stranded inhibitory molecules are denatured undercertain conditions such that the complementary single stranded moleculeswhich are hybridized are allowed to separate. Single stranded moleculesformed do not interact or bind polymerase or interact or bind polymerasewith reduced efficiency compared to the corresponding double-strandedmolecule.

Unit

The term “unit” as used herein refers to the activity of an enzyme. Whenreferring, for example, to a DNA polymerase, one unit of activity is theamount of enzyme that will incorporate 10 nanomoles of dNTPs intoacid-insoluble material (i.e., DNA or RNA) in 30 minutes under standardprimed DNA synthesis conditions.

Viruses

As used herein, viruses that require a reverse transcriptase activity tocomplete their lifecycle are seen to include, but are not limited to,any member of the family retroviridae including human immunodeficiencyviruses, bovine immunodeficiency virus, bovine leuukemia virus, humanT-lymphotrophic viruses, caprine arthritis-encephalitis virus, equineinfectious anemia virus, feline immunodeficiency virus, feline sarcomaand leukemia viruses, maedi/visna virus of sheep, mouse mammary tumorvirus, simian immunodeficiency virus and other retroviruses known tothose skilled in the art.

Vector

The term “vector” as used herein refers to a plasmid, phagemid, cosmidor phage nucleic acid or other nucleic acid molecule which is able toreplicable autonomously in a host cell. Preferably a vector ischaracterized by one or a small number of restriction endonucleaserecognition sites at which such nucleic acid sequences may be cut in adeterminable fashion without loss of an essential biological function ofthe vector, and into which nucleic acid molecules may be spliced inorder to bring about its replication and cloning. The cloning vector mayfurther contain one or more markers suitable for use in theidentification of cells transformed with the cloning vector. Markers,for example, are antibiotic resistance change genes, including, but notlimited to tetracycline resistance or ampicillin resistance.

Expression Vector

The term “expression vector” as used herein refers to avector similar toa cloning vector but which is capable of enhancing the expression of agene which has been cloned into it, after transformation into a host.The cloned gene is usually placed under the control of (i.e., operablylinked to) certain control sequences such as promoter sequences.

Recombinant Host

The term “recombinant host” as used herein refers to any prokaryotic oreukaryotic microorganism which contains the desired cloned genes in anexpression vector, cloning vector or any other nucleic acid molecule.The term “recombinant host” is also meant to include those host cellswhich have been genetically engineered to contain the desired gene on ahost chromosome or in the host genome.

Host

The term “host” as used herein refers to any prokaryotic or eukaryoticmicroorganism that is the recipient of a replicable expression vector,cloning vector or any nucleic acid molecule including the inhibitorynucleic acid molecules of the invention. The nucleic acid molecule maycontain, but is not limited to, a structural gene, a promoter and/or anorigin of replication.

Promoter

The term “promote” as used herein refers to a DNA sequence generallydescribed as the 5′ region of a gene, located proximal to start thecodon. At the promoter region, transcription of an adjacent gene(s) isinitiated.

Gene

The term “gene” as used herein refers to a DNA sequence that containsinformation necessary for expression of a polypeptide or protein. Itincludes the promoter and the structural gene as well as other sequencesinvolved in expression of the protein.

Structural Gene

The term “structural gene” as used herein refers to a DNA sequence thatis transcribed into messenger RNA that is then translated into asequence of amino acids characteristic of a specific polypeptide.

Operably Linked

The term “operably linked” as used herein means that the promoter ispositioned to control the initiation of expression of the polypeptideencoded by the structural gene.

Expression

The term “expression” has used herein refers to the process by which agene produces a polypeptide. It includes transcription of the gene intomessenger RNA (mRNA) and the translation of such mRNA intopolypeptide(s).

Substantially Pure

As used herein “substantially pure” means that the desired purifiedmolecule such as a protein or nucleic acid molecule (including theinhibitory nucleic acid molecule of the invention) is essentially freefrom contaminants which are typically associated with the desiredmolecule. Contaminating components may include, but are not limited to,compounds or molecules which may interfere with the inhibitory orsynthesis reactions of the invention, and/or that degrade or digest theinhibitory nucleic acid molecules of the invention (such as nucleasesincluding exonucleases and endonucleases) or that degrade or digest thesynthesized or amplified nucleic acid molecules produced by the methodsof the invention.

Thermostable

As used herein “thermostable” refers to a DNA polymerase which is moreresistant to inactivation by heat. DNA polymerases synthesize theformation of a DNA molecule complementary to a single-stranded DNAtemplate by extending a primer in the 5′-3′-direction. This activity formesophilic DNA polymerases may be inactivated by heat treatment. Forexample, T5 DNA polymerase activity is totally inactivated by exposingthe enzyme to a temperature of 90° C. for 30 seconds. As used herein, athermostable DNA polymerase activity is more resistant to heatinactivation than a mesophilic DNA polymerase. However, a thermostableDNA polymerase docs not mean to refer to an enzyme which is totallyresistant to heat inactivation and thus heat treatment may reduce theDNA polymerase activity to some extent. A thermostable DNA polymerasetypically will also have a higher optimum temperature than mesophilicDNA polymerases.

3-to-5′ Exonuclease Activity

“3′-to-5′ exonuclease activity” is an enzymatic activity well known tothe art. This activity is often associated with DNA polymerases and isthought to be involved in a DNA replication “editing” or correctionmechanism.

A “DNA polymerase substantially reduced in 3′-to-5′ exonucleaseactivity” is defined herein as either (1) a mutated DNA polymerase thathas about or less than 10%, or preferably about or less than 1%, of the3′-to-5′ exonuclease activity of the corresponding unmutated, wild-typeenzyme, or (2) a DNA polymerase having a 3′-to-5′ exonuclease specificactivity which is less than about 1 unit/mg protein, or preferably aboutor less than 0.1 units/mg protein. A unit of activity of 3′-to-5′exonuclease is defined as the amount of activity that solubilizes 10nmoles of substrate ends in 60 min. at 37° C., assayed as described inthe “BRL 1989 Catalogue & Reference Guide”, page 5, with HhaI fragmentsof lambda DNA 3′-end labeled with [³H]dTTP by terminal deoxynucleotidyltransferase (TdT). Protein is measured by the method of Brandford, Anal.Biochem. 72:248 (1976). As a means of comparison, natural, wild-typeT5-DNA polymerase (DNAP) or T5-DNAP encoded by pTTQ19-T5-2 has aspecific activity of about 10 units/mg protein while the DNA polymeraseencoded by pTTQ19-T5-2(Exo-) (U.S. Pat. No. 5,270,179) has a specificactivity of about 0.0001 units/mg protein, or 0.001% of the specificactivity of the unmodified enzyme, a 10₅-fold reduction. Polymerasesused in accordance with the invention may lack or may be substantiallyreduced in 3′ exonuclease activity.

5′-to-3′ Exonuclease Activity

“5′-to-3′ exonuclease activity” is also enzymatic activity well known inthe art. This activity is often associated with DNA polymerases, such asE. coli PolI and Taq DNA polymerase.

A “polymerase substantially reduced in 5′-to-3′ exonuclease activity” isdefined herein as either (1) mutated or modified polymerase that hasabout or less than 10%, or preferably about or less than 1%, of the5′-to-3′ exonuclease activity of the corresponding unmutated, wild-typeenzyme, or (2) a polymerase having 5′-to-3′ exonuclease specificactivity which is less than about 1 unit/mg protein, or preferably aboutor less than 0.1 units/mg protein.

Both of the 3′-to-5′ and 5′-to-3′ exonuclease activities can be observedon sequencing gels. Active 5′-to-3′ exonuclease activity will producedifferent size products in a sequencing gel by removing mono-nucleotidesand longer products from the 5′-end of the growing primers. 3′-to-5′exonuclease activity can be measured by following the degradation ofradiolabeled primers in a sequencing gel. Thus, the relative amounts ofthese activities (e.g., by comparing wild-type and mutant or modifiedpolymerases) can be determined with no more than routineexperimentation.

Inhibitory Nucleic Acids

The nucleic acids of the present invention include single stranded anddouble stranded nucleic acids (although other strand multiples such astriple stranded (e.g., triple helix) molecules may be used) includingnucleic acids comprised of DNA, RNA, PNA, LNA or other derivativenucleic acid molecules, or a combination thereof. The inhibitory nucleicacid comprises a sequence which is capable of forming a site at one setof conditions (preferably at ambient temperature) which competes withthe template/primer substrate used in synthesis or amplification forbinding an enzyme with polymerase activity and competes less efficientlyunder a second set of conditions (preferably elevated temperatures) fornucleic acid synthesis or amplification. Preferably, the sequence of theinhibitory nucleic acids is not complementary to the primer used in thesynthesis, amplification or sequencing reaction to be inhibited. As willbe recognized, other nucleic acids (natural, unnatural, modified etc.)may be selected and used in accordance with the invention. Suchselection may be accomplished by binding studies and/or nucleic acidsynthesis inhibition assays. Design of nucleic acid sequences forhairpin formation may be accomplished by those skilled in the art. See,e.g., Antao, V. P. and Tinoco, I., Jr., 1992, Nucl. Acids Res. 20:819-824. Preferably, the nucleic acid inhibitor could be made nucleaseresistant (3′-to-5′ exonuclease and 5′-to-3′ exonuclease) and/or inertto polymerization. Methods to render the nucleic acid inert toexonucleases and polymerization are known in the art and include, forexample, using derivative nucleic acid molecules which may includederivative nucleotides (for example, using phosphamide and/orphosphorothioate backbone rather than phosphate) and/or addition of oneor more blocking agents to the inhibitory nucleic acid molecules of theinvention. The inhibitory nucleic acid preferably form one or morehairpin-loop structures with a double stranded stem. The double strandedstem can have blunt ends and/or a single stranded overhang (for example,at the 5′ and/or 3′ terminus) designed so as to mimic the typicalprimer/template substrate of a polymerase.

Inhibitory nucleic acids of the present invention are preferably used inthe present compositions and methods at a final concentration in asynthesis, sequencing or amplification reaction sufficient to prevent orinhibit such synthesis, sequencing or amplification in the presence of apolymerase or reverse transcriptase enzyme. The ratio of inhibitorynucleic acids of the invention to polymerase or reverse transcriptasemay vary depending on the polymerase or reverse transcriptase used. Themolar ratio of inhibitory nucleic acids to polymerase/reversetranscriptase enzyme for a synthesis, sequencing or amplificationreaction may range from about 0.001-100:1; 0.01-1000:1; 0.1-10,000:1;1-100,000:1; 1-500,000:1; or 1-1,000,000:1. Of course, other suitableratios of such inhibitory nucleic acids to polymerase/reversetranscriptase suitable for use in the invention will be apparent to oneof ordinary skill in the art or determined with no more than routineexperimentation.

Inhibitory nucleic acid molecules of the invention may be synthesized bystandard chemical oligonucleotide synthesis techniques (for example,phosphoramidite and others know in the art, see U.S. Pat. No.5,529,756). Alternatively, recombinant DNA techniques may be used toproduce the inhibitory nucleic acids of the invention by cloning thenucleic acid molecule of interest into a vector, introducing the vectorinto the host cell, growing the host cell and isolating the inhibitorynucleic acid molecule of interest from the host cell. Inhibitory nucleicacid molecules of the invention may also be obtained from commercialsources of custom oligonucleotides such as Life Technologies, Inc. ormay be made enzymaticly, for example, by using polymerases in nucleicacid synthesis or amplification reactions.

In some embodiments, the oligonucleotides of the present invention maybe used for therapeutic purposes. In a preferred embodiment, theoligonucleotides of the present invention may be used to treat a subject(for example, a human or an animal) infected with a virus that requiresreverse transcriptase activity to replicate. For therapeutic treatment,oligonucleotides may be administered as a pharmaceutically acceptablecomposition in which one or more oligonucleotides of the presentinvention may be mixed with one or more carriers, thickeners, diluents,buffers, preservatives, surface active agents, excipients and the like.Pharmaceutical compositions may also include one or more additionalactive ingredients such as antimicrobial agents, antiinflammatoryagents, anesthetics, and the like in addition to oligonucleotides.

The pharmaceutical compositions of the present invention may beadministered by any route commonly used to administer pharmaceuticalcompositions. For example, administration may be done topically(including opthalmically, vaginally, rectally, intranasally), orally, byinhalation, or parenterally, for example by intravenous drip orsubcutaneous, intraperitoneal or intramuscular injection.

Pharmaceutical compositions formulated for topical administration mayinclude ointments, lotions, creams, gels, drops, suppositories, sprays,liquids and powders. Any conventional pharmaceutical excipient, such ascarriers, aqueous, powder or oily bases, thickeners and the like may beused.

Pharmaceutical compositions formulated for oral administration may be inthe form of one or more powders, granules, suspensions or solutions inwater or non-aqueous media, capsules, sachets, or tablets.Pharmaceutical compositions formulated for oral administration mayadditionally comprise thickeners, flavorings, diluents, emulsifiers,dispersing aids, binders or the like.

Pharmaceutical compositions formulated for parenteral administration mayinclude sterile aqueous solutions which may also contain buffers,diluents and other suitable additives.

The pharmaceutical compositions of the present invention may beadministered in a therapeutically effective dose. A therapeuticallyeffective dose is one which inhibits the replication of the virus withinthe host. It is not necessary that replication of the virus be entirelyeliminated in order for a treatment to be therapeutically effective.Reduction of the rate of replication of the virus may be a therapeuticeffect. One or more doses of the pharmaceutical compositions of thepresent invention may be administered one or more times daily for aperiod of treatment which may be a single administration or may bemultiple administrations per day for a period of several days to severalmonths or until a cure is effected or a diminution of disease state isachieved. Persons of ordinary skill can easily determine optimumdosages, dosing routes and the frequency at which doses should beadministered.

Polymerases. Enzymes with polymerase activity to which the inhibitorynucleic acids of the present invention can bind or interact include anyenzyme used in nucleic acid synthesis, amplification or sequencingreactions. Such polymerases include, but are not limited to, polymerases(DNA and RNA polymerases), and reverse transcriptases. DNA polymerasesinclude, but are not limited to, Thermus thermophilus (Tth) DNApolymerase, Thermus aquaticus (Taq) DNA polymerase, Thermotoganeopolitana (Tne) DNA polymerase, Thermotoga maritima (Tma) DNApolymerase, Thermococcus litoralis (Tli or VENT™) DNA polymerase,Pyrococcus furiosus (Pfu) DNA polyernase, DEEPVENT™ DNA polymerase,Pyrococcus woosii (Pwo) DNA polymerase, Pyrococcus sp KOD2 (KOD) DNApolymerase, Bacillus sterothermophilus (Bst) DNA polymerase, Bacilluscaldophilus (Bca) DNA polymerase, Sulfolobus acidocaldarius (Sac) DNApolyermase, Thermoplasma acidophilum (Tac) DNA polymerase, Thermusflavus (Tfl/Tub) DNA polymerase, Thermus ruber (Tru) DNA polymerase,Thermus brockianus (DYNAZYME™) DNA polymerase, Methanobacteriumthermoautotrophicum (Mth) DNA polymerase, mycobacterium DNA polymerase(Mtb, Mlep), E. coli polI DNA polymerase, T5 DNA polymerase, T7 DNApolymerase, and generally polI type DNA polymerases and mutants,variants and derivatives thereof. RNA polymerases such as T3, T5 and SP6and mutants, variants and derivatives thereof may also be used inaccordance with the invention.

The nucleic acid polymerases used in the present invention may bemesophilic or thermophilic, and are preferably thermophilic. Preferredmesophilic DNA polymerases include polI family of DNA polymerases (andtheir respective Klenow fragments) any of which may be isolated fromorganism such as E. coli, H. influenzae, D. radiodurans, H. pylori, C.aurantiacus, R. Prowazekii, T pallidum, Synechocysis sp., B. subtilis,L. lactis, S. pneumoniae, M. tuberculosis, M. leprae, M. smegmatis,Bacteriophage L5, phi-C31, T7, T3, T5, SP01, SP02, mitochondrial from S.cerevisiae MIP-1, and eukaryotic C. elegans, and D. melanogaster(Astatke, M. et al., 1998, J. Mol Biol. 278, 147-165), polIII type DNApolymerase isolated from any sources, and mutants, derivatives orvariants thereof, and the like. Preferred thermostable DNA polymerasesthat may be used in the methods and compositions of the inventioninclude Taq, Tne, Tma, Pfu, KOD, Tfl, Tth Stoffel fragment, VENT™ andDEEPVENT™ DNA polymerases, and mutants, variants and derivatives thereof(U.S. Pat. Nos. 5,436,149; 4,889,818; 4,965,188; 5,079,352; 5,614,365;5,374,553; 5,270,179; 5,047,342; 5,512,462; WO 92/06188; WO 92/06200; WO96/10640; WO 97/09451; Barnes, W. M. Gene 112:29-35 (1992); Lawyer, F.C., et al, PCR Meth. Appl. 2:275-287 (1993); Flaman, J.-M, et al., Nucl.Acids Res. 22(15):3259-3260 (1994)).

Reverse transcriptases for use in this invention include any enzymehaving reverse transcriptase activity. Such enzymes include, but are notlimited to, retroviral reverse transcriptase, retrotransposon reversetranscriptase, hepatitis B reverse transcriptase, cauliflower mosaicvirus reverse transcriptase, bacterial reverse transcriptase, Tth DNApolymerase, Taq DNA polymerase (Saiki, R. K., et al, Science 239:487-491(1988); U.S. Pat. Nos. 4,889,818 and 4,965,188), Tne DNA polymerase (WO96/10640 and WO 97/09451), Tma DNA polymerase (U.S. Pat. No. 5,374,553)and mutants, variants or derivatives thereof (see, e.g., WO 97/09451 andWO 98/47912). Preferred enzymes for use in the invention include thosethat have reduced, substantially reduced or eliminated RNase H activity.By an enzyme “substantially reduced in RNase H activity” is meant thatthe enzyme has less than about 20%, more preferably less than about 15%,10% or 5%, and most preferably less than about 2%, of the RNase Hactivity of the corresponding wildtype or RNase H+ enzyme such aswildtype Moloney Murine Leukemia Virus (M-MLV), Avian MyeloblastosisVirus (AMV) or Rous Sarcoma Virus (RSV) reverse transcriptases. TheRNase H activity of any enzyme may be determined by a variety of assays,such as those described, for example, in U.S. Pat. No. 5,244,797, inKotewicz, M. L., et al, Nucl. Acids Res. 16:265 (1988) and in Gerard, G.F., et al., FOCUS 14(5):91 (1992), the disclosures of all of which arefully incorporated herein by reference. Particularly preferredpolypeptides for use in the invention include, but are not limited to,M-MLV H⁻ reverse transcriptase, RSV H⁻ reverse transcriptase, AMV H⁻reverse transcriptase, RAV (rous-associated virus) H⁻ reversetranscriptase, MAV (myeloblastosis-associated virus) H⁻ reversetranscriptase and HIV H⁻ reverse transcriptase. (See U.S. Pat. No.5,244,797 and WO 98/47912). It will be understood by one of ordinaryskill, however, that any enzyme capable of producing a DNA molecule froma ribonucleic acid molecule (i.e., having reverse transcriptaseactivity) may be equivalently used in the compositions, methods and kitsof the invention.

The enzymes having polymerase activity for use in the invention may beobtained commercially, for example from Life Technologies, Inc.(Rockville, Md.), Perkin-Elmer (Branchburg, N.J.), New England BioLabs(Beverly, Mass.) or Boehringer Mannheim Biochemicals (Indianapolis,Ind.). Enzymes having reverse transcriptase activity for use in theinvention may be obtained commercially, for example, from LifeTechnologies, Inc. (Rockville, Md.), Pharmacia (Piscataway, N.J.), Sigma(Saint Louis, Mo.) or Boehringer Mannheim Biochemicals (Indianapolis,Ind.). Alternatively, polymerases or reverse transcriptases havingpolymerase activity may be isolated from their natural viral orbacterial sources according to standard procedures for isolating andpurifying natural proteins that are well-known to one of ordinary skillin the art (see, e.g., Houts, G. E., et al., j. Virol. 29:517 (1979)).In addition, such polymerases/reverse transcriptases may be prepared byrecombinant DNA techniques that are familiar to one of ordinary skill inthe art (see, e.g., Kotewicz, M. L., et al., Nucl. Acids Res. 16:265(1988); U.S. Pat. No. 5,244,797; WO 98/47912; Soltis, D. A., and Skalka,A. M., Proc. Natl. Acad Sci. USA 85:3372-3376 (1988)). Examples ofenzymes having polymerase activity and reverse transcriptase activitymay include any of those described in the present application.

Methods of Nucleic Acid Synthesis, Amplification and Sequencing

The inhibitory nucleic acids and compositions of the invention may beused in methods for the synthesis of nucleic acids. In particular, ithas been discovered that the present inhibitory nucleic acids andcompositions reduce nonspecific nucleic acid synthesis, particularly inamplification reactions such as the polymerase chain reaction (PCR). Thepresent inhibitory nucleic acids and compositions may therefore be usedin any method requiring the synthesis of nucleic acid molecules, such asDNA (including cDNA) and RNA molecules. Methods in which the inhibitorynucleic acids or compositions of the invention may advantageously beused include, but are not limited to, nucleic acid synthesis methods andnucleic acid amplification methods (including “hot-start” synthesis oramplification) where the reaction is set up at a temperature where theinhibitory nucleic acid can competitively inhibit DNA synthesis oramplification and the synthesis or amplification reaction is initiatedby increasing the temperature to reduce the competitive inhibition bythe inhibitor of the polymerases thus allowing nucleic acid synthesis oramplification to take place.

Nucleic acid synthesis methods according to this aspect of the inventionmay comprise one or more steps. For example, the invention provides amethod for synthesizing a nucleic acid molecule comprising (a) mixing anucleic acid template with one or more primers and one or moreinhibitory nucleic acids of the present invention (which may be the sameor different) and one or more enzymes having polymerase or reversetranscriptase activity to form a mixture; (b) incubating the mixtureunder conditions sufficient to inhibit or prevent nucleic acidsynthesis; and (c) incubating the mixture under conditions sufficient tomake a first nucleic acid molecule complementary to all or a portion ofthe template. According to this aspect of the invention, the nucleicacid template may be a DNA molecule such as a cDNA molecule or library,or an RNA molecule such as a mRNA molecule or population of molecules.Conditions sufficient to allow synthesis such as pH, temperature, ironicstrength, and incubation times may be optimized according to routinemethods known to those skilled in the art.

In accordance with the invention, the input or template nucleic acidmolecules or libraries may be prepared from populations of nucleic acidmolecules obtained from natural sources, such as a variety of cells,tissues, organs or organisms. Cells that may be used as sources ofnucleic acid molecules may be prokaryotic (bacterial cells, includingthose of species of the genera Escherichia, Bacillus, Serratia,Salmonella, Staphylococcus, Streptococcus, Clostridium, Chlamydia,Neisseria, Treponema, Mycoplasma, Borrelia, Legionella, Pseudomonas,Mycobacterium, Helicobacter, Erwinia, Agrobacterium, Rhizobium, andStreptomyces) or eukaryotic (including fungi (especially yeasts),plants, protozoans and other parasites, and animals including insects(particularly Drosophilia spp. cells), nematodes (particularlyCaenorhabditis elegans cells), and mammals (particulary human cells)).

Once the starting cells, tissues, organs or other samples are obtained,nucleic acid molecules (such as DNA, RNA (e.g., mRNA or polyA+RNA)molecules) may be isolated, or cDNA molecules or libraries preparedtherefrom, by methods that are well-known in the art (See, e.g.Maniatis, T., et al., Cell 15:687-701 (1978); Okayama, H., and Berg, P.,Mol. Cell. Biol. 2:161-170 (1982); Gubler, U., and Hoffman, B. J., Gene25:263-269 (1983)).

In the practice of a preferred aspect of the invention, a first nucleicacid molecule may be synthesized by mixing an nucleic acid templateobtained as described above, which is preferably a DNA molecule or anRNA molecule such as an mRNA molecule or a polyA+RNA molecule, with oneor more of the above-described enzymes with polymerase activity to whichhas been added the inhibitory nucleic acids or compositions of theinvention to form a mixture. Synthesis of a first nucleic acid moleculecomplementary to all or a portion of the nucleic acid template ispreferably accomplished after raising the temperature of the reactionand thus reducing the competitive inhibition of the inhibitory nucleicacid of the present invention thereby favoring the reverse transcription(in the case of an RNA template) and/or polymerization of the input ortemplate nucleic acid molecule. Such synthesis is preferablyaccomplished in the presence of nucleotides (e.g., deoxyribonucleosidetriphosphates (dNTPs), dideoxyribonucleoside triphosphate (ddNTPs) orderivatives thereof).

Of course, other techniques of nucleic acid synthesis in which theinhibitory nucleic acids, compositions and methods of the invention maybe advantageously used will be readily apparent to one of ordinary skillin the art.

In other aspects of the invention, the inhibitory nucleic acids andcompositions of the invention may be used in methods for amplifying orsequencing nucleic acid molecules. Nucleic acid amplification methodsaccording to this aspect of the invention may additionally comprise useof one or more polypeptides having reverse transcriptase activity, inmethods generally known in the art as one-step (e.g., one-step RT-PCR)or two-step (e.g., two-step RT-PCR) reverse transcriptase-amplificationreactions. For amplification of long nucleic acid molecules (e.g.,greater than about 3-5 Kb in length), a combination of DNA polymerasesmay be used, as described in WO 98/06736 and WO 95/16028.

Amplification methods according to this aspect of the invention maycomprise one or more steps. For example, the invention provides a methodfor amplifying a nucleic acid molecule comprising (a) mixing one or moreenzymes with polymerase activity with the inhibitory nucleic acids orcompositions of the invention and one or more nucleic acid templates;(b) incubating the mixture under conditions sufficient to inhibit orprevent nucleic acid amplification; and (c) incubating the mixture underconditions sufficient to allow the enzyme with polymerase activity toamplify one or more nucleic acid molecules complementary to all or aportion of the templates. The invention also provides nucleic acidmolecules amplified by such methods.

General methods for the amplification and analysis of nucleic acidmolecules or fragments are well-known to one of ordinary skill in theart (see e.g., U.S. Pat. Nos. 4,683,195; 4,683,202; and 4,800,159;Innis, M. A., et al., eds., PCR Protocols: A Guide to Methods andApplications, San Diego, Calif.: Academic Press, Inc. (1990); Griffin,H. G., and Griffin, A. M., eds., PCR Technology: Current Innovations,Boca Raton, Fla.: CRC Press (1994)). For example, amplification methodswhich may be used in accordance with the present invention include PCR(U.S. Pat. Nos. 4,683,195 and 4,683,202), Strand DisplacementAmplification (SDA; U.S. Pat. No. 5,455,166; EP 0 684 315), Nucleic AcidSequenced-Based Amplification (NASBA; U.S. Pat. No. 5,409,818; EP 0 329822).

Typically, these amplification methods comprise: (a) mixing one or moreenzymes with polymerase activity with one or more inhibitory nucleicacids of the present invention to form a complex (protein-nucleic acid);(b) mixing the nucleic acid sample with the complex of (a) in thepresence of one or more primer sequences; and (c) amplifying the nucleicacid sample to generate a collection of amplified nucleic acidfragments, preferably by PCR or equivalent automated amplificationtechnique.

Following amplification or synthesis by the methods of the presentinvention, the amplified or synthesized nucleic acid fragments may beisolated for further use or characterization. This step is usuallyaccomplished by separation of the amplified or synthesized nucleic acidfragments by size or by any physical or biochemical means including gelelectrophoresis, capillary electrophoresis, chromatography (includingsizing, affinity and immunochromatography), density gradientcentrifugation and immunoadsorption. Separation of nucleic acidfragments by gel electrophoresis is particularly preferred, as itprovides a rapid and highly reproducible means of sensitive separationof a multitude of nucleic acid fragments, and permits direct,simultaneous comparison of the fragments in several samples of nucleicacids. One can extend this approach, in another preferred embodiment, toisolate and characterize these fragments or any nucleic acid fragmentamplified or synthesized by the methods of the invention. Thus, theinvention is also directed to isolated nucleic acid molecules producedby the amplification or synthesis methods of the invention.

In this embodiment, one or more of the amplified or synthesized nucleicacid fragments are removed from the gel which was used foridentification (see above), according to standard techniques such aselectroelution or physical excision. The isolated unique nucleic acidfragments may then be inserted into standard vectors, includingexpression vectors, suitable for transfection or transformation of avariety of prokaryotic (bacterial) or eukaryotic (yeast, plant or animalincluding human and other mammalian) cells. Alternatively, nucleic acidmolecules produced by the methods of the invention may be furthercharacterized, for example by sequencing (e.g., determining thenucleotide sequence of the nucleic acid fragments), by methods describedbelow and others that are standard in the art (see, e.g., U.S. Pat. Nos.4,962,022 and 5,498,523, which are directed to methods of DNAsequencing).

Nucleic acid sequencing methods according to the invention may compriseone or more steps. For example, the invention provides a method forsequencing a nucleic acid molecule comprising (a) mixing an enzyme withpolymerase activity with one or more inhibitory nucleic acids of thepresent invention, a nucleic acid molecule to be sequenced, one or moreprimers, one or more nucleotides, and one or more terminating agents(such as a dideoxynucleotide) to form a mixture; (b) incubating themixture under conditions sufficient to inhibit or prevent nucleic acidsequencing or synthesis; (c) incubating the mixture under conditionssufficient to synthesize a population of molecules complementary to allor a portion of the molecule to be sequenced; and (d) separating thepopulation to determine the nucleotide sequence of all or a portion ofthe molecule to be sequenced.

Nucleic acid sequencing techniques which may employ the presentinhibitory molecules or compositions include dideoxy sequencing methodssuch as those disclosed in U.S. Pat. Nos. 4,962,022 and 5,498,523.

Vectors and Host Cells

The present invention also relates to vectors which comprise aninhibitory nucleic acid molecule of the present invention. Further, theinvention relates to host cells which contain the inhibitory nucleicacids of the invention and preferably to host cells comprisingrecombinant vectors containing such nucleic acids, and to methods forthe production of the nucleic acids of the invention using these vectorsand host cells. Nucleic acid synthesis and amplification productsproduced by the methods of the invention may also be cloned into vectorsand host cells in accordance with the invention to facilitate productionof such nucleic acid molecules or proteins encoded by such nucleic acidmolecules.

The vectors will preferably include at least one selectable marker. Suchmarkers include, but are not limited to, antibiotic resistance genessuch as tetracycline or ampicillin resistance genes for culturing in E.coli and other bacteria.

Representative examples of appropriate host cells include, but are notlimited to, bacterial cells such as E. coli, Streptomyces spp., Erwiniaspp., Klebsiella spp and Salmonella typhimurium. Preferred as a hostcell is E. coli, and particularly preferred are E. coli strains DH10Band Stb12, which are available commercially (Life Technologies, Inc.,Rockville, Md.).

Nucleic Acid Production

As noted above, the methods of the present invention are suitable forproduction of any nucleic acid or any protein encoded by such nucleicacid molecule, via insertion of the above-described nucleic acidmolecules or vectors into a host cell and isolation of the nucleic acidmolecule from the host cell or isolation of the protein from the hostcell expressing the nucleic acid molecule. Introduction of the nucleicacid molecules or vectors into a hot cell to produce a transformed hostcell can be effected by calcium phosphate transfection, calcium chloridetransformation, DEAE-dextran mediated transfection, cationiclipid-mediated transfection, electroporation, transduction, infection orother methods. Such methods are described in many standard laboratorymanuals, such as Davis, et al, Basic Methods in Molecular Biology(1986). Preferably, chemically competent or electrocompetent cells areused for such transformation reactions. Once transformed host cells havebeen obtained, the cells may be cultivated under any physiologicallycompatible conditions of pH and temperature, in any suitable nutrientmedium containing assimilable sources of carbon, nitrogen and essentialminerals that support host cell growth. For example, certain expressionvectors comprise regulatory regions which require cell growth at certaintemperatures, or addition of certain chemicals or inducing agents to thecell growth. Appropriate culture media and conditions for theabove-described host cells and vectors are well-known in the art.Following its production in the host cells, the nucleic acid or proteinof interest may be isolated by several techniques. To liberate thenucleic acid or protein of interest from the host cells, the cells arepreferably lysed or ruptured. This lysis may be accomplished bycontacting the cells with a hypotonic solution, by treatment with a cellwall-disrupting enzyme such as lysozyme, by sonication, by treatmentwith high pressure, or by a combination of the above methods. Othermethods of bacterial cell disruption and lysis that are known to one ofordinary skill may also be used.

Following disruption, the nucleic acid or proteins may be separated fromthe cellular debris by any technique suitable for separation ofparticles in complex mixtures. The nucleic acids or proteins may then bepurified by well known isolation techniques. Suitable techniques forpurification include, but are not limited to, ammonium sulfate orethanol precipitation, acid extraction, electrophoresis,immunoadsorption, CsCl centrifugation, anion or cation exchangechromatography, phosphocellulose chromatography, hydrophobic interactionchromatography, affinity chromatography, immunoaffinity chromatography,size exclusion chromatography, liquid chromatography (LC), highperformance LC (HPLC), fast performance LC (FPLC), hybroxylapatitechromatography and lectin chromatography.

Kits

The present invention also provides kits for use in the synthesis,amplification or sequencing of nucleic acid molecules. Kits according tothis aspect of the invention may comprise one or more containers, suchas vials, tubes, ampules, bottles and the like, which may comprise oneor more of the inhibitory nucleic acids and/or compositions of theinvention.

The kits of the invention may comprise one or more of the followingcomponents: (i) one or more nucleic acids or compositions of theinvention; (ii) one or more polymerases and/or reverse transcriptases,(iii) one or more suitable buffers or buffering salts; (iv) one or morenucleotides; and (v) one or more primers.

It will be readily apparent to one of ordinary skill in the relevantarts that other suitable modifications and adaptations to the methodsand applications described herein are obvious and may be made withoutdeparting from the scope of the invention or any embodiment thereof.Having now described the present invention in detail, the same will bemore clearly understood by reference to the following examples, whichare included herewith for purposes of illustration only and are notintended to be limiting of the invention.

EXAMPLE 1 Nucleic Acid Inhibitors

Nucleic acid inhibitors were synthesized by Life Technologies, Inc. andwere HPLC or PAGE purified.

Nucleic Acid Inhibitor A (34-mer)

^(5′)CCCAATATGGACCGGTCGAAAGACCGGTCCATAT^(3′) (SEQ ID NO:1)

Nucleic Acid Inhibitor B (55-mer)

^(5′)CCATGCAGGTAGCCGATGAACTGGTCGAAAGACCAGTTCATCGGCTACCTGCATG^(3′) (SEQID NO:2)

At ambient temperature the above sequences form a hairpin-like structure(Antao an dTinoco, 1992, supra), see structures below.

In some embodiments, the 3′-terminus of Inhibitor A may be capped at the3′ terminus with a dideoxythymine triphosphate using a Klenow fragmentmutatn (F762Y) of DNA polymerase I (Escherichia coli) or T7 DNApolymerase (Tabor, S. and Richardson, C. C., 1995, Proc. Natl. Acad Sci.USA 92, 6339-6343). The 3′-OH terminus of the oligonucleotide wasextended with ddTTP by the polymerase at 20 μM ddTTP in the presence of2 mM Mg2⁺ in 50 mM Tris pH 7.5 buffer, at 37° C. for 30 min. Followingextension, the sample was placed in a 100° C. water bath for 3 min todenature the protein. Following heating the oligonucleotide sample wascooled slowly to ambient temperature (2-3 hrs) to allow formation of thehairpin structure.

Nucleic Acid Inhibitor A as Hairpin Structure:

 A (SEQ ID NO:1) A GACCGGTCCATAT A CTGGCCAGGTATAACCC^(5′)  G

Nucleic Acid Inhibitor B as Hairpin Structure

 A (SEQ ID NO:2) A GACCAGTTCATCGGCTACCTGCATG ACTGGTCAAGTAGCCGATGGACGTACC^(5′)  G

In some embodiments, the nucleic acid inhibitor B may be capped at the3′ terminus by ddGTP as described above.

This invention was tested using Tne DNA polymerase—a thermostable DNApolymerase that is significantly efficient at low temperature inincorporating deoxynucleotides into the growing strand, about 50-foldmore efficient than Taq DNA polymerase at 37° C. The Tne used was wildtype except that it was rendered substantially reduced in 5′ to 3′exonuclease activity by virtue of D137A mutation (See WO 98/09451).

EXAMPLE 2 Inhibition of Polymerase with Inhibitor

The time course of the activity of Tne DNA polymerase was qualitativelydetermined using a 34/60-mer primer/template substrate at 3 differenttemperatures. FIG. 1 represents results from these experiments. For eachtemperature, polymerase activity was measured in the absence (Panel A)and presence (Panel B) of inhibitor A. Aliquots of the reaction mixturewere taken at various time points and separated on an agarose gel. Thefive lanes, of each panel, from left to right at 15 sec, 30 sec, 1 min,2 min and 5 min, time points that have elapsed before the reactions werequenched. P and C denote the primer position and control lane,respectively.

As can be seen in FIG. 1, the potency of the inhibition of thepolymerase reaction catalyzed by Tne is significantly reduced as thetemperature is increased.

EXAMPLE 3 Amplification of a Target DNA Sequence from Plasmid DNA Source

A 2.7 Kb target DNA sequence delivered from pUC19 plasmid was amplifiedusing 5 different dilutions of the template. The target was amplified byTne DNA polymerases. Two different concentration of Tne polymerase (85nM (e.g., 1 unit) and 42.5 nM (i.e., 0.5 units) and the Tne complexed tothe inhibitor nucleic acid (using a 150-fold excess inhibitor B overpolymerase) were used at each amplification condition. The results areshown in FIG. 2. The concentration of the target DNA in lanes 1, 2, 3, 4and 5 denote 100 pg, 20 pg 2 pg, 0.2 pg and 0.02 pg, respectively.

Results indicate that the sensitivity of Tne was greatly improved by theaddition of the inhibitor, and relative purity of the target moleculewas immensely enhanced.

EXAMPLE 4 Amplification of a Target DNA Sequence from Genomic DNA Source

A 1 Kb, 3 Kb and 5 Kb target DNA sequences were amplified by Tne (85 nM(e.g., 1 unit) and Taq (1 unit) DNA polymerases as represented in panelsA, B and C of FIG. 3, respectively. The four lanes of each panelrepresented as a, b, c and d are Tne (+125-fold excess inhibitor A (ddTcapped)), Tne (+50-fold excess inhibitor A (ddT capped)), Tne (noinhibitor) and Taq (no inhibitor), respectively.

Results indicate that the sensitivity of Tne was greatly improved by theaddition of the inhibitor and relative purity of the target molecule wasimmensely improved for each target condition.

EXAMPLE 5 Amplification of a 5 and 15 Kb Target DNA Sequence by Tne DNAPolymerase

The five panels A, B, C, D and E of FIG. 4 represent reactionconditions: control Tne (no inhibitor), Tne (+50-fold excess inhibitorB), Tne (+150-fold excess inhibitor B), Tne (+300-fold excess inhibitorB), Tne (+750-fold excess inhibitor B), respectively. The two lanes ineach panel represented as A and B are for amplification of target sizeof 5 and 15 Kb. The final concentration of the Tne DNA polymerase ineach reaction was 8.5 nM (e.g., 0.1 unit).

As can be seen in FIG. 4, the sensitivity of Tne was greatly improved bythe addition of this inhibitor, and relative purity of the targetmolecule was immensely improved as the concentration of the inhibitorwas optimized. As shown in panels D and E, 15 Kb product can only beamplified by Tne DNA polymerase, under Taq PCR conditions(Perkin-Elmer), in the presence of the inhibitor nucleic acid.

EXAMPLE 6 Amplification of a 3 Kb Target DNA Sequence (Human GenomicSource) by 1 Unit Taq

DNA Polymerase

The three panels A, B, and C of FIG. 5 represent reaction conditions.For A and B, the same primer sequences were used. In A, the PCR mix wasincubated at 94° C. for 1 min and was set on ice to force mis-priming.All PCR reaction were set for 30 min at 25° C. so as to increasenon-specific DNA synthesis. Each condition: lane A (Taq control), B(Taq+126 nM inhibitor), C (Taq+32 nM inhibitor) and D (Taq+64 nMinhibitor).

Results show that the specificity of Taq was greatly improved by theaddition of the inhibitor in each case producing significant reductionin the non-specific DNA synthesis and enhanced amount of the targetsequence product.

EXAMPLE 7 Inhibition of RT Using the Oligonucleotides of the PresentInvention

The DNA polymerase activity of ThermoScript™ I RNase deficient mutantreverse transcriptase (RT) (available from Life Technologies, Inc.) wasdetermined at ambient temperature, 37° C. and 55° C. in the presence andabsence of the oligonucleotide inhibitor molecules. The sequences andsecondary structures of the oligonucleotide inhibitors are shown below.The polymerase activity of the RT was determined under steady statekinetic conditions using olig(dG)₁₅/polyrC as the primer/templatesubstrate. This assay has been described by Polesky et al. (1990), andwas used with minor modification.

Oligonucleotide Inhibitors

All nucleic acid inhibitors used in our assays were HPLC purified, andwere capped synthetically with phosphate (PO⁴⁻) at the 3′ terminus. Themis-matches on the double stranded portion of the molecules wereintroduced in order to reduce the melting temperature of the doublestranded without affecting the length of the nucleic acid inhibitors.Nucleic acid inhibitor H is a control oligonucleic acid that does notform double stranded structure under our experimental condition and isused to determine the level of inhibition by the RNA sequence.

Nucleic Acid Inhibitor C (Synthesized by Synthetic Genetics)

A 17/27 mer DNA/DNA double stranded nucleic acid inhibitor.

^(5′)GGTATAGTAATAATATA^(3′)

^(3′)CCATATCATTATTATATATGTAATTAA^(5′) (SEQ ID NO:3)

Nucleic Acid Inhibitor D (Synthesized by Life Technologies, Inc.)

A 50 mer Dna/RNA hybrid nucleic acid, RNA bases are underlined.

^(5′) AAUUAAUGUAUAUAUUAUUACUAUACCGAAGGGTATAGTAATAATATATA^(5′) (SEQ IDNO:4)

Hairpin Structure of Nucleic Acid Inhibitor D

 G (SEQ ID NO:4) A GGTATAGTAATAATATATA^(-3′) ACCAUAUCAUUAUUAUAUAUGUAAUUAA ^(-5′)  G

Nucleic Acid Inhibitor E (Synthesized by Life Technologies, Inc.)

A 50 mer DNA/RNA hybrid nucleic acid, RNA bases are single underline andthe two mis-match positions are double underlined on the DNA portion ofthe corresponding hairpin structure.

^(5′) AAUUAAUGUAUAUAUUAUUACUAUACCGAAGGGTATAATAATAGTATATA^(3′) (SEQ IDNO:5)

Hairpin Structure of Nucleic Acid Inhibitor E

 G (SEQ ID NO:5) A GGTATAATAATAGTATATA^(-3′) ACCAUAUCAUUAUUAUAUAUGUAAUUAA ^(-5′)  G

Nucleic Acid Inhibitor F (Synthesized by Life Technologies, Inc.)

A 50 mer DNA/RNA hybrid nucleic acid, RNA bases are single underlinedand the three mis-match positions are double underlined on the DNAportion of the corresponding hairpin structure.

^(5′) AAUUAAUGUAUAUAUUAUUACUAUACCGAAGGGTATAATGAGAGTATATA^(3′) (SEQ IDNO:6)

Hairpin Structure of Nucleic Acid Inhibitor F

 G (SEQ ID NO:6) A GGTATAATGAGAGTATATA^(-3′) ACCAUAUCAUUAUUAUAUAUGUAAUUAA ^(-5′)  G

Nucleic Acid Inhibitor G (Synthesized by Life Technologies, Inc.

A 50 mer DNA/RNA hybrid nucleic acid, RNA bases are underlined and thefour mis-match positions are double underlined on the DNA portion of thecorresponding hairpin structure.

⁵′AAUUAAUGUAUAUAUUAUUACUAUACCGAAGGGTATAATGAGAGTATATA^(3′) (SEQ ID NO:7)

Hairpin Structure of Nucleic Acid Inhibitor G

 G (SEQ ID NO:7) A GGTATAATGAGAGTATATA^(-3′) ACCAUAUCAUUAUUAUAUAUGUAAUUAA^(-5′)  G

Nucleic Acid Inhibitor H (Synthesized by Life Technologies, Inc.)

A 50 mer DNA/RNA hybrid nucleic acid, RNA bases are underlined.

^(5′) AAUUAAUGUAUAUAUUAUUACUAUACCGAAAATATATAATGATGATATAG^(3′) (SEQ IDNO:8)

The relative polymerase activities of ThermoScript™ I in the absence andpresence of nucleic acid inhibitors at ambient temperature (˜22° C.),37° C. and 55° C was determined. The polymerization reaction wasinitiated by the addition of RT or RT/inhibitor (5 μL) to a solution ofthe primer/template in the presence of dGTP (spiked with dGT³²P) andMgCl₂, final reaction volume of 50 μL. The mixture was incubated at thereaction temperature, and samples (5 μL) were removed at 1 min (22° C.)and 15 sec (37° C. and 55° C.) intervals and were added into 50 μL of 25mM EDTA. A portion of the quenched solution was applied to DE-81filters. Following washes to remove unincorporated dGTP, the filterswere counted in scintillation vials containing EconoFluor-2 (Packard).The apparent rate of the reaction was derived from the rate plot (cornplotted against time interval). The reaction concentration of theoligo(dG)₁₅/polyrC was 800 nM in primer, dGTP was 100 μM and MgCl₂ andKCl were 10 mM and 50 mM, respectively. For each reaction condition theconcentration of the reverse transcriptase was maintained at 12 nMwhereas the concentration of each of the oligonucleotide inhibitor was540 nM.

The relative activity of the polymerization reaction catalyzed byThermoScript™ at ambient temperature, 37° C. and 55° C. in the presenceand absence of the inhibitors are shown in FIGS. 6A and 6B. Theactivities in the absence of the oligonucleotide inhibitors (freeThermoScript™ I) was normalized to 1 for measurements at eachtemperature. The RT activity in the presence of an inhibitor wascorrelated to the activity of ThermoScript™ at each temperature and therelative normalized activities are presented as a bar graph and areshown in FIGS. 6A and 6B. For each set of reaction condition, the threebars from left to right denote reactions performed at ambienttemperature, 37° C. and 55° C., respectively. TS, TS-D, TS-E, and TS-Hin FIG. 6A denote polymerase reaction initiated by ThermoScript™ I,ThermoScript™ I-nucleic acid inhibitor D complex, ThermoScript™I-nucleic acid inhibitor E complex and ThermoScript™ I-nucleic acidinhibitor H complex, respectively. The efficiency of inhibition of theRT activity is dependent to the temperature which indicates that thelevel of inhibition of RT by the nucleic acid inhibitors is dependent tothe melting temperature of the nucleic acid.

Nucleic Acid Inhibitor D

Under experimental conditions described above, complexing ThermoScript™I with about 50-fold excess of this nucleic acid prior to initiating thepolymerization reaction inhibited the RT activity by about 85-90% ateach of the reaction temperatures. The relative similarity of the levelof inhibition is indicative of the stability of the hairpin structure ofthis nucleic acid inhibitor in the temperature range that was assayedfor RT activity.

Nucleic Acid Inhibitor E

Under the experimental conditions, complexing ThermoScript™ I with about50-fold excess of this nucleic acid prior to initiating thepolymerization reaction inhibited the RT activity by about 90% atambient temperature and 37° C. but the level of inhibition was 45% at55° C. The significant reduction in the level of inhibition at 55° C.suggests that the hairpin structure was destabilized by the introductionof the two mismatches. This result suggests that “hot-start” of thepolymerase reaction catalyzed by reverse transcriptases can be enhancedby using a nucleic acid inhibitor that forms double stranded at ambienttemperature but denatures at the desired polymerization temperature.

Nucleic Acid Inhibitor H

Under the experimental conditions, complexing ThermoScript™ I with about50-fold excess of this nucleic acid prior to initiating thepolymerization reaction inhibition the RT activity by about 50% atambient temperature. The level of inhibition at 37° C. and 55° C. wasnegligible, within our experimental error. This result suggests thatthere is a background level of inhibition at ambient temperature that isnot derived from the primer/template substrate competition. Whereas thelevel of inhibition by the addition of inhibitor H was minimal at 37° C.and 55° C., under our experimental condition.

The relative polymerase activities of Thermoscript™ I in the absence andpresence of the remaining nucleic acid inhibitors described above areshown in FIG. 6B. For each set of reaction conditions, the three barsfrom left to right denote reactions performed at ambient temperature,37° C. and 55° C., respectively. TS, TS-C, TS-H, TS-E, TS-F and TS-Gdenote polymerase reaction initiated by ThermoScript™ I, ThermoScript™I-nucleic acid inhibitor C complex, ThermoScript™ I-nucleic acidinhibitor H complex, ThermoScript™ I-nucleic acid inhibitor E complex,ThermoScript™ I-nucleic acid inhibitor F complex, and ThermoScript™I-nucleic acid inhibitor G complex, respectively.

Nucleic Acid Inhibitor C

Under the experimental conditions, complexing ThermoScript™ I with about50-fold excess of this nucleic acid (DNA/DNA) prior to initiating thepolymerase inhibited the RT activity by about 70% at each of thereaction temperature. The relative similarity of the level of inhibitionis indicative of the stability of the double stranded structure of thisnucleic acid sequence in the temperature range in which the RT activitywas assayed.

Nucleic Acid Inhibitor H

Under the experimental conditions, complexing ThermoScript™ I with about50-fold excess of this nucleic acid prior to initiating thepolymerization reaction inhibited the RT activity by about 400/o atambient temperature. The level of inhibition at 37° C. and 55° C. wasnegligible, within our experimental error.

Nucleic Acid Inhibitor E

Under the experimental conditions, complexing ThermoScript™ I with about50-fold excess of this nucleic acid prior to initiating thepolymerization reaction inhibited the RT activity by more than 90% atambient temperature and 37° C. but the level of inhibition was 60% at55° C.

Nucleic Acid Inhibitor F

Under the experimental conditions, complexing ThermoScript™ I with about50-fold excess of this nucleic acid prior to initiating thepolymerization reaction inhibited the RT activity by about 80% atambient temperature, 65% at 37° C. and 40% at 55° C. The decrease in thelevel of inhibition in correlation to the increase of the reactiontemperature is indicative of the destabilization of the hairpinstructure due to the three mismatches.

Nucleic Acid Inhibitor G

Under the experimental conditions, complexing ThermoScript™ I with about50-fold excess of this nucleic acid prior to initiating thepolymerization reaction inhibited the RT activity by about 80% atambient temperature, 55% at 37° C. and 30% at 55° C. The decrease in thelevel of inhibition in correlation to the increase of the reactiontemperature is indicative of the destabilization of the hairpinstructure due to the three mismatches.

EXAMPLE 8 Inhibition of Reverse Transcriptase Activity within a Cell

The oligonucleotides of the present invention may be used to inhibit theactivity of a revere transcriptase enzyme with a cell. Oligonucleotidesfor use inside a cell may optionally be modified to render themresistant to one or more nuclease enzymes that may be present in a cell.For example, a derivative of the nucleic acid inhibitor may besynthesized with one or more of the following modifications: 1) one ormore of the ribose groups on the RNA portion of the oligonucleotide maybe alkylated, for example, methylated, preferably at the 2′-OH toproduce a 2′-O methyl; 2) one or more of the internucleotide linkages ofthe oligonucleotide, for example, in the DNA portion of the nucleicacid, may contain a modified linkage, for example, a phosphorothioatelinkage; 3) the 3′ terminus of the oligonucleotide may be capped so asto be non-extendable, for example, with a phosphate, phoshorothioate ora dideoxynucleotide or other modification of the 3′-hydroxyl so as tomake it not extendable. Other modification that increase the level ofresistance to cellular RNase activity and/or reduce the efficiency ofDNA degradation by other cellular factors are known to those skilled inthe art and may be incorporated into the design of the oligonucleotidesof the present invention. In addition to rendering the oligonucleotidesresistant to one or more cellular degradation factors, phosphorothioatereduces the possibility of homologous recombination into the hostchromosome should a given inhibitor contain a region homologous to oneon the host chromosome.

Oligonucleotides may be assayed to determine if they have an inhibitoryeffect on reverse transcriptase activity in a cell. Cells to be treatedwith the oligonucleotides of the invention, for example NIH3T3 cells maybe transfected with the nucleic acid (Life Technologies, Inc.) using anymethod known to those skilled in the art. In some preferred embodiments,the oligonucleotides of the invention may be introduced into the cellsusing lipid mediated transfection (see, for example, U.S. Pat. Nos.5,334,761; 5,674,908; 5,627,159; 5,736,392; 5,279,833 and publishedinternational application WO 94/27345 all of which are specificallyincorporated herein by reference).

Following transfection of the cells, a virus expressing a reversetranscriptase (for example, Moloney Murine Leukemia V, M-MLV) may beadded so as to efficiently infect cells with the virus and provide asource of reverse transcriptase activity. (Jolicoeur, P. and Rassart,E., 1980). An aliquot of the cells will be centrifuged and lysed at timeintervals in order to assay for reverse transcriptase activity.Comparing the level of RT activity derived from cells that aretransfected with a nucleic acid inhibitor and those that are nottransfected, the efficacy of inhibition of viral proliferation in thecell can be determined.

EXAMPLE 9 Inhibition of Taq Polymerase Using PhosphorothioateSubstituted Oligonucleotides

In some preferred embodiments, one or more phosphorothioate residues maybe incorporated into the oligonucleotides of the present invention.Those skilled in the art will appreciate that oligonucleotidesincorporating such internucleotide linkages may be more resistant tonuclease activities that may be present in a reaction mixture or withina cell. Accordingly, such modifications may be made in oligonucleotidesintended for in vivo or in vitro use. In some preferred embodiments, allof the internucleotide linkages may be phosphorotioate linkages.

In some embodiments, the 3′-terminus of an oligonucleotide of theinvention may be modified to render the oligonucleotide more resistantto any 3′-to 5′-exonuclease activity present in a reaction mixture orwithin a cell. In some embodiments, the 3′-hydroxyl of theoligonucleotide may be modified, for example, by coupling a spacermodifier to the hydroxyl group. Such spacer modifiers are commerciallyavailable (Glen Research) and may comprise a chain of carbon atoms whichmay be substituted with one or more groups containing heteroatoms. Insome preferred embodiments, the 3′-hydroxyl of the oligonucleotides ofthe invention may be modified with a 3 carbon spacer which terminates ina group containing a heteroatom such as, for example, an amine group ora hydroxyl group. The incorporation of such spacer modifiers into anoligonucleotide may be accomplished using chemistries well known tothose skilled in the art for example, by the incorporation of a suitablyblocked phophoramidite version of the spacer.

To examine the effectiveness of phosphorothioate modifiedoligonucleotides to inhibit Taq polymerase oligonucleotides wereconstructed in which all phosphate internucleotide linkages were changeto phophorothioate internucleotide linkages. Four such oligonucleotideswere constructed and their sequences are given below. HPHH1 is aphosphorothioate hairpin oligonucleotide with a 3 nucleotide loop, amelting temperature of the duplex region of 59° C. and a ΔG=−15.70kcal/mol of formation of the duplex.

HPHH2 is a phosphorothioate hairpin oligonucleotide with a 3 nucleotideloop, a melting temperature of the duplex region of 67° C. and aΔG=−18.10 kcal/mol of formation of the duplex.

HPHH3 is a phosphorothioate hairpin oligonucleotide with a 5 nucleotideloop and a melting temperature of the duplex region of 70° C. and aΔG=−18.90 kcal/mol of formation of the duplex.

HPHH4 is a phosphorothioate oligonucleotide with a 4 nucleotide loop anda melting temperature of 65° C. of the duplex and a ΔG=−13.5 kcal/mol offormation of the duplex.

The bases involved in formation of the stem structure are indicated by avertical line. When the oligonucleotide was modified at the 3′-terminalwith a 3 carbon spacer group ending in a hydroxyl, the designation Sspa3was added to the name of oligonucleotide.

With reference to FIG. 7, amplification reactions to produce a 1.6 kb(A), a 2 kb (B) and a 2.6 kb (C) fragment of the NF2 gene. In eachpanel, lane a is the amplification using Taq polymerase alone, lane b isthe amplification reaction in the presence of inhibitor HPHH4Sspa3 at amolar ratio of 1.2:1 inhibitor: polymerase and lane c is theamplification using Platinum Taq. The template was 200 ng of genomicDNA. A comparison of lane b to lanes a and c in each panel shows thatthe presence of the inhibitor improves the amount of full length productand reduces the amount of shorter products under these reactionconditions.

As shown in FIG. 8, the activity of Taq polymerase in a nucleotideincorporation assay was determined at three temperatures (25° C., 55° C.and 72° C.) in the presence of two different concentrations of inhibitorHPHH4Sspa3 (molar ratios of 2:1 and 7.5:1 inhibitor:polymerase). At eachtemperature, the solid black bar is the Taq polymerase alone, thestriped bar is Taq polymerase plus inhibitor at a 2:1 ratio of inhibitorto polymerase and the solid white bar is Taq plus inhibitor at a 7.5:1ratio of inhibitor:polymerase. The incorporation was assayed in a PCRreaction mixture incubated at the indicated temperature in the presenceof alpha-[³²P]-dCTP. After 30 minutes, the reactions were stopped by theaddition of EDTA and an aliquot of each reaction was spotted onto GF/Cfilters. The filters were washed with TCA and counted. The activity wasnormalized to the amount of activity of the Taq polymerase at the sametemperature.

At 25° C. and a 2:1 ratio, Taq activity was reduced to approximately 60%of the un-inhibited polymerase while a 7.5:1 ratio reduced activity byapproximately 90%. At 55° C. (a typical annealing temperature)inhibition was still observed, approximately a 20% and 60% reduction inactivity at 2:1 and 7.5:1 respectively. At 72° C. (a typical extensiontemperature) inhibition was nearly eliminated at a 2.5:1 ratio and wasapproximately 50% at a 7.5:1 ratio. These data indicate that theinhibition is temperature dependent with more inhibition observed atlower temperatures (i.e., when the oligonucleotide is in a hairpinstructure) and less at a higher temperature.

The concentration dependence of the inhibition of Taq polymerase byinhibitor HPHHSspa3 was studied at 37° C. and the results are shown inFIG. 9. The incorporation assay described above was used. These resultsindicate that the inhibition is dose dependent with a slight (20%)inhibition seen at a molar ration of 0.5:1 inhibitor: polymerase up to anearly complete inhibition (96%) seen at 7.5:1. By way of comparison, aTaq polymerase inhibited by antibody (Platinum Taq) was tested under thesame conditions. At a molar ratio of 7.5:1, the inhibitors of thepresent invention provide a comparable amount of inhibition of Taqactivity as the antibody.

Having now fully described the present invention in some detail by wayof illustration and example for purposes of clarity of understanding, itwill be obvious to one of ordinary skill in the art that the same can beperformed by modifying or changing the invention within a wide andequivalent range of conditions, formulations and other parameterswithout affecting the scope of the invention or any specific embodimentthereof, and that such modifications or changes are intended to beencompassed within the scope of the appended claims.

All publications, patents and patent applications mentioned in thisspecification are indicative of the level of skill of those skilled inthe art to which this invention pertains, and are herein incorporated byreference to the same extent as if each individual publication, patentor patent application was specifically and individually indicated to beincorporated by reference.

12 1 34 DNA Artificial Sequence Description of Artificial Sequencenucleic acid inhibitor 1 cccaatatgg accggtcgaa agaccggtcc atat 34 2 55DNA Artificial Sequence Description of Artificial Sequence nucleic acidinhibitor 2 ccatgcaggt agccgatgaa ctggtcgaaa gaccagttca tcggctacct gcatg55 3 44 DNA Artificial Sequence Description of Artificial Sequencenucleic acid inhibitor 3 aattaatgta tatattatta ctataccggt atagtaataatata 44 4 50 DNA Artificial Sequence Description of Combined DNA/RNAMolecule RNA bases from 1-25 and DNA bases from 26-50 4 aauuaauguauauauuauua cuauaccgaa gggtatagta ataatatata 50 5 50 DNA ArtificialSequence Description of Combined DNA/RNA Molecule RNA bases from 1 to 25and DNA bases from 25-48 5 aauuaaugua uauauuauua cuauaccgaa gggtataataatagtatata 50 6 50 DNA Artificial Sequence Description of CombinedDNA/RNA Molecule RNA bases from 1-25 and DNA bases from 26-50 6aauuaaugua uauauuauua cuauaccgaa gggtataatg agagtatata 50 7 50 DNAArtificial Sequence Description of Combined DNA/RNA Molecule RNA basesfrom 1-25 and DNA bases from 26-50 7 aauuaaugua uauauuauua cuauaccgaagggtataatg agagtatata 50 8 50 DNA Artificial Sequence Description ofCombined DNA/RNA Molecule RNA bases from 1-25 and DNA bases from 26-50 8aauuaaugua uauauuauua cuauaccgaa aatatataat gatgatatag 50 9 38 DNAArtificial Sequence Description of Artificial Sequence syntheticoligonucleotides 9 cggatgtatt aactatcaat acaattgata gttaagac 38 10 38DNA Artificial Sequence Description of Artificial Sequence syntheticoligonucleotides 10 cggatggatt aactatcaat acaattgata gttaatcc 38 11 40DNA Artificial Sequence Description of Artificial Sequence syntheticoligonucleotides 11 cggatggatt aactatcaat tacagattga tagttaatcc 40 12 35DNA Artificial Sequence Description of Artificial Sequence syntheticoligonucleotides 12 acatgtattg atagatcgac aagatctatc aatac 35

What is claimed is:
 1. A method of preparing cDNA from mRNA, comprising:mixing one or more mRNA templates with one or more reversetranscriptases, and with one or more double stranded inhibitory nucleicacids; and incubating said mixture under conditions sufficient tosynthesize one or more cDNA molecules complementary to all or a portionof said templates.
 2. The method of claim 1, wherein said mixing isaccomplished under conditions sufficient to prevent nucleic acidsynthesis and/or allow binding of said one or more double strandedinhibitory nucleic acids to said reverse transcriptase.